diff --git a/apps/encryption/appinfo/application.php b/apps/encryption/appinfo/application.php
index 75107b2723..515a408fa2 100644
--- a/apps/encryption/appinfo/application.php
+++ b/apps/encryption/appinfo/application.php
@@ -30,6 +30,7 @@ use OCA\Encryption\Controller\RecoveryController;
 use OCA\Encryption\Controller\SettingsController;
 use OCA\Encryption\Controller\StatusController;
 use OCA\Encryption\Crypto\Crypt;
+use OCA\Encryption\Crypto\DecryptAll;
 use OCA\Encryption\Crypto\EncryptAll;
 use OCA\Encryption\Crypto\Encryption;
 use OCA\Encryption\HookManager;
@@ -113,7 +114,9 @@ class Application extends \OCP\AppFramework\App {
 				$container->query('Crypt'),
 				$container->query('KeyManager'),
 				$container->query('Util'),
+				$container->query('Session'),
 				$container->query('EncryptAll'),
+				$container->query('DecryptAll'),
 				$container->getServer()->getLogger(),
 				$container->getServer()->getL10N($container->getAppName())
 			);
@@ -242,6 +245,18 @@ class Application extends \OCP\AppFramework\App {
 			}
 		);
 
+		$container->registerService('DecryptAll',
+			function (IAppContainer $c) {
+				return new DecryptAll(
+					$c->query('Util'),
+					$c->query('KeyManager'),
+					$c->query('Crypt'),
+					$c->query('Session'),
+					new QuestionHelper()
+				);
+			}
+		);
+
 	}
 
 	public function registerSettings() {
diff --git a/apps/encryption/lib/crypto/decryptall.php b/apps/encryption/lib/crypto/decryptall.php
new file mode 100644
index 0000000000..599cd82aa4
--- /dev/null
+++ b/apps/encryption/lib/crypto/decryptall.php
@@ -0,0 +1,143 @@
+<?php
+/**
+ * @author Björn Schießle <schiessle@owncloud.com>
+ *
+ * @copyright Copyright (c) 2015, ownCloud, Inc.
+ * @license AGPL-3.0
+ *
+ * This code is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License, version 3,
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ */
+
+
+namespace OCA\Encryption\Crypto;
+
+
+use OCA\Encryption\KeyManager;
+use OCA\Encryption\Session;
+use OCA\Encryption\Util;
+use Symfony\Component\Console\Helper\QuestionHelper;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Output\OutputInterface;
+use Symfony\Component\Console\Question\ConfirmationQuestion;
+use Symfony\Component\Console\Question\Question;
+
+class DecryptAll {
+
+	/** @var Util  */
+	protected $util;
+
+	/** @var QuestionHelper  */
+	protected $questionHelper;
+
+	/** @var  Crypt */
+	protected $crypt;
+
+	/** @var  KeyManager */
+	protected $keyManager;
+
+	/** @var Session  */
+	protected $session;
+
+	/**
+	 * @param Util $util
+	 * @param KeyManager $keyManager
+	 * @param Crypt $crypt
+	 * @param Session $session
+	 * @param QuestionHelper $questionHelper
+	 */
+	public function __construct(
+		Util $util,
+		KeyManager $keyManager,
+		Crypt $crypt,
+		Session $session,
+		QuestionHelper $questionHelper
+	) {
+		$this->util = $util;
+		$this->keyManager = $keyManager;
+		$this->crypt = $crypt;
+		$this->session = $session;
+		$this->questionHelper = $questionHelper;
+	}
+
+	/**
+	 * prepare encryption module to decrypt all files
+	 *
+	 * @param InputInterface $input
+	 * @param OutputInterface $output
+	 * @param $user
+	 * @return bool
+	 */
+	public function prepare(InputInterface $input, OutputInterface $output, $user) {
+
+		$question = new Question('Please enter the recovery key password: ');
+		$recoveryKeyId = $this->keyManager->getRecoveryKeyId();
+
+		if (!empty($user)) {
+			$questionUseLoginPassword = new ConfirmationQuestion(
+				'Do you want to use the users login password to decrypt all files? (y/n) ',
+				false
+			);
+			$useLoginPassword = $this->questionHelper->ask($input, $output, $questionUseLoginPassword);
+			if ($useLoginPassword) {
+				$question = new Question('Please enter the users login password: ');
+			} else if ($this->util->isRecoveryEnabledForUser($user) === false) {
+				$output->writeln('No recovery key available for user ' . $user);
+				return false;
+			} else {
+				$user = $recoveryKeyId;
+			}
+		} else {
+			$user = $recoveryKeyId;
+		}
+
+		$question->setHidden(true);
+		$question->setHiddenFallback(false);
+		$password = $this->questionHelper->ask($input, $output, $question);
+		$privateKey = $this->getPrivateKey($user, $password);
+		if ($privateKey !== false) {
+			$this->updateSession($user, $privateKey);
+			return true;
+		} else {
+			$output->writeln('Could not decrypt private key, maybe you entered the wrong password?');
+		}
+
+
+		return false;
+	}
+
+	/**
+	 * get the private key which will be used to decrypt all files
+	 *
+	 * @param string $user
+	 * @param string $password
+	 * @return bool|string
+	 * @throws \OCA\Encryption\Exceptions\PrivateKeyMissingException
+	 */
+	protected function getPrivateKey($user, $password) {
+		$recoveryKeyId = $this->keyManager->getRecoveryKeyId();
+		if ($user === $recoveryKeyId) {
+			$recoveryKey = $this->keyManager->getSystemPrivateKey($recoveryKeyId);
+			$privateKey = $this->crypt->decryptPrivateKey($recoveryKey, $password);
+		} else {
+			$userKey = $this->keyManager->getPrivateKey($user);
+			$privateKey = $this->crypt->decryptPrivateKey($userKey, $password, $user);
+		}
+
+		return $privateKey;
+	}
+
+	protected function updateSession($user, $privateKey) {
+		$this->session->prepareDecryptAll($user, $privateKey);
+	}
+}
diff --git a/apps/encryption/lib/crypto/encryption.php b/apps/encryption/lib/crypto/encryption.php
index c62afac83c..fde4a2c4a9 100644
--- a/apps/encryption/lib/crypto/encryption.php
+++ b/apps/encryption/lib/crypto/encryption.php
@@ -30,6 +30,7 @@ namespace OCA\Encryption\Crypto;
 
 use OC\Encryption\Exceptions\DecryptionFailedException;
 use OCA\Encryption\Exceptions\PublicKeyMissingException;
+use OCA\Encryption\Session;
 use OCA\Encryption\Util;
 use OCP\Encryption\IEncryptionModule;
 use OCA\Encryption\KeyManager;
@@ -75,6 +76,9 @@ class Encryption implements IEncryptionModule {
 	/** @var Util */
 	private $util;
 
+	/** @var  Session */
+	private $session;
+
 	/** @var  ILogger */
 	private $logger;
 
@@ -87,25 +91,34 @@ class Encryption implements IEncryptionModule {
 	/** @var  bool */
 	private $useMasterPassword;
 
+	/** @var DecryptAll  */
+	private $decryptAll;
+
 	/**
 	 *
 	 * @param Crypt $crypt
 	 * @param KeyManager $keyManager
 	 * @param Util $util
+	 * @param Session $session
 	 * @param EncryptAll $encryptAll
+	 * @param DecryptAll $decryptAll
 	 * @param ILogger $logger
 	 * @param IL10N $il10n
 	 */
 	public function __construct(Crypt $crypt,
 								KeyManager $keyManager,
 								Util $util,
+								Session $session,
 								EncryptAll $encryptAll,
+								DecryptAll $decryptAll,
 								ILogger $logger,
 								IL10N $il10n) {
 		$this->crypt = $crypt;
 		$this->keyManager = $keyManager;
 		$this->util = $util;
+		$this->session = $session;
 		$this->encryptAll = $encryptAll;
+		$this->decryptAll = $decryptAll;
 		$this->logger = $logger;
 		$this->l = $il10n;
 		$this->useMasterPassword = $util->isMasterKeyEnabled();
@@ -150,7 +163,15 @@ class Encryption implements IEncryptionModule {
 		$this->isWriteOperation = false;
 		$this->writeCache = '';
 
-		$this->fileKey = $this->keyManager->getFileKey($this->path, $this->user);
+		if ($this->session->decryptAllModeActivated()) {
+			$encryptedFileKey = $this->keyManager->getEncryptedFileKey($this->path);
+			$shareKey = $this->keyManager->getShareKey($this->path, $this->session->getDecryptAllUid());
+			$this->fileKey = $this->crypt->multiKeyDecrypt($encryptedFileKey,
+				$shareKey,
+				$this->session->getDecryptAllKey());
+		} else {
+			$this->fileKey = $this->keyManager->getFileKey($this->path, $this->user);
+		}
 
 		if (
 			$mode === 'w'
@@ -426,6 +447,19 @@ class Encryption implements IEncryptionModule {
 		$this->encryptAll->encryptAll($input, $output);
 	}
 
+	/**
+	 * prepare module to perform decrypt all operation
+	 *
+	 * @param InputInterface $input
+	 * @param OutputInterface $output
+	 * @param string $user
+	 * @return bool
+	 */
+	public function prepareDecryptAll(InputInterface $input, OutputInterface $output, $user = '') {
+		return $this->decryptAll->prepare($input, $output, $user);
+	}
+
+
 	/**
 	 * @param string $path
 	 * @return string
diff --git a/apps/encryption/lib/session.php b/apps/encryption/lib/session.php
index c3759c3fc5..1d0c371148 100644
--- a/apps/encryption/lib/session.php
+++ b/apps/encryption/lib/session.php
@@ -25,6 +25,7 @@
 
 namespace OCA\Encryption;
 
+use OCA\Encryption\Exceptions\PrivateKeyMissingException;
 use \OCP\ISession;
 
 class Session {
@@ -106,6 +107,61 @@ class Session {
 		$this->session->set('privateKey', $key);
 	}
 
+	/**
+	 * store data needed for the decrypt all operation in the session
+	 *
+	 * @param string $user
+	 * @param string $key
+	 */
+	public function prepareDecryptAll($user, $key) {
+		$this->session->set('decryptAll', true);
+		$this->session->set('decryptAllKey', $key);
+		$this->session->set('decryptAllUid', $user);
+	}
+
+	/**
+	 * check if we are in decrypt all mode
+	 *
+	 * @return bool
+	 */
+	public function decryptAllModeActivated() {
+		$decryptAll = $this->session->get('decryptAll');
+		return ($decryptAll === true);
+	}
+
+	/**
+	 * get uid used for decrypt all operation
+	 *
+	 * @return string
+	 * @throws \Exception
+	 */
+	public function getDecryptAllUid() {
+		$uid = $this->session->get('decryptAllUid');
+		if (is_null($uid) && $this->decryptAllModeActivated()) {
+			throw new \Exception('No uid found while in decrypt all mode');
+		} elseif (is_null($uid)) {
+			throw new \Exception('Please activate decrypt all mode first');
+		}
+
+		return $uid;
+	}
+
+	/**
+	 * get private key for decrypt all operation
+	 *
+	 * @return string
+	 * @throws PrivateKeyMissingException
+	 */
+	public function getDecryptAllKey() {
+		$privateKey = $this->session->get('decryptAllKey');
+		if (is_null($privateKey) && $this->decryptAllModeActivated()) {
+			throw new PrivateKeyMissingException('No private key found while in decrypt all mode');
+		} elseif (is_null($privateKey)) {
+			throw new PrivateKeyMissingException('Please activate decrypt all mode first');
+		}
+
+		return $privateKey;
+	}
 
 	/**
 	 * remove keys from session
@@ -114,7 +170,9 @@ class Session {
 		$this->session->remove('publicSharePrivateKey');
 		$this->session->remove('privateKey');
 		$this->session->remove('encryptionInitialized');
-
+		$this->session->remove('decryptAll');
+		$this->session->remove('decryptAllKey');
+		$this->session->remove('decryptAllUid');
 	}
 
 }
diff --git a/apps/encryption/tests/lib/SessionTest.php b/apps/encryption/tests/lib/SessionTest.php
index e036c43993..0fa48666d7 100644
--- a/apps/encryption/tests/lib/SessionTest.php
+++ b/apps/encryption/tests/lib/SessionTest.php
@@ -56,6 +56,7 @@ class SessionTest extends TestCase {
 	 * @depends testSetAndGetPrivateKey
 	 */
 	public function testIsPrivateKeySet() {
+		$this->instance->setPrivateKey('dummyPrivateKey');
 		$this->assertTrue($this->instance->isPrivateKeySet());
 
 		unset(self::$tempStorage['privateKey']);
@@ -65,6 +66,51 @@ class SessionTest extends TestCase {
 		self::$tempStorage['privateKey'] = 'dummyPrivateKey';
 	}
 
+	public function testDecryptAllModeActivated() {
+		$this->instance->prepareDecryptAll('user1', 'usersKey');
+		$this->assertTrue($this->instance->decryptAllModeActivated());
+		$this->assertSame('user1', $this->instance->getDecryptAllUid());
+		$this->assertSame('usersKey', $this->instance->getDecryptAllKey());
+	}
+
+	public function testDecryptAllModeDeactivated() {
+		$this->assertFalse($this->instance->decryptAllModeActivated());
+	}
+
+	/**
+	 * @expectedException \Exception
+	 * @expectExceptionMessage 'Please activate decrypt all mode first'
+	 */
+	public function testGetDecryptAllUidException() {
+		$this->instance->getDecryptAllUid();
+	}
+
+	/**
+	 * @expectedException \Exception
+	 * @expectExceptionMessage 'No uid found while in decrypt all mode'
+	 */
+	public function testGetDecryptAllUidException2() {
+		$this->instance->prepareDecryptAll(null, 'key');
+		$this->instance->getDecryptAllUid();
+	}
+
+	/**
+	 * @expectedException \OCA\Encryption\Exceptions\PrivateKeyMissingException
+	 * @expectExceptionMessage 'Please activate decrypt all mode first'
+	 */
+	public function testGetDecryptAllKeyException() {
+		$this->instance->getDecryptAllKey();
+	}
+
+	/**
+	 * @expectedException \OCA\Encryption\Exceptions\PrivateKeyMissingException
+	 * @expectExceptionMessage 'No key found while in decrypt all mode'
+	 */
+	public function testGetDecryptAllKeyException2() {
+		$this->instance->prepareDecryptAll('user', null);
+		$this->instance->getDecryptAllKey();
+	}
+
 	/**
 	 *
 	 */
@@ -112,6 +158,10 @@ class SessionTest extends TestCase {
 	 *
 	 */
 	public function testClearWillRemoveValues() {
+		$this->instance->setPrivateKey('privateKey');
+		$this->instance->setStatus('initStatus');
+		$this->instance->prepareDecryptAll('user', 'key');
+		$this->assertNotEmpty(self::$tempStorage);
 		$this->instance->clear();
 		$this->assertEmpty(self::$tempStorage);
 	}
@@ -138,4 +188,9 @@ class SessionTest extends TestCase {
 
 		$this->instance = new Session($this->sessionMock);
 	}
+
+	protected function tearDown() {
+		self::$tempStorage = [];
+		parent::tearDown();
+	}
 }
diff --git a/apps/encryption/tests/lib/crypto/decryptalltest.php b/apps/encryption/tests/lib/crypto/decryptalltest.php
new file mode 100644
index 0000000000..d6a52fe97c
--- /dev/null
+++ b/apps/encryption/tests/lib/crypto/decryptalltest.php
@@ -0,0 +1,125 @@
+<?php
+/**
+ * @author Björn Schießle <schiessle@owncloud.com>
+ *
+ * @copyright Copyright (c) 2015, ownCloud, Inc.
+ * @license AGPL-3.0
+ *
+ * This code is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License, version 3,
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ */
+
+
+namespace OCA\Encryption\Tests\lib\Crypto;
+
+
+use OCA\Encryption\Crypto\Crypt;
+use OCA\Encryption\Crypto\DecryptAll;
+use OCA\Encryption\KeyManager;
+use OCA\Encryption\Session;
+use OCA\Encryption\Util;
+use Symfony\Component\Console\Helper\QuestionHelper;
+use Test\TestCase;
+
+class DecryptAllTest extends TestCase {
+
+	/** @var  DecryptAll */
+	protected $instance;
+
+	/** @var Util | \PHPUnit_Framework_MockObject_MockObject  */
+	protected $util;
+
+	/** @var KeyManager | \PHPUnit_Framework_MockObject_MockObject  */
+	protected $keyManager;
+
+	/** @var  Crypt | \PHPUnit_Framework_MockObject_MockObject */
+	protected $crypt;
+
+	/** @var  Session | \PHPUnit_Framework_MockObject_MockObject */
+	protected $session;
+
+	/** @var QuestionHelper | \PHPUnit_Framework_MockObject_MockObject  */
+	protected $questionHelper;
+
+	public function setUp() {
+		parent::setUp();
+
+		$this->util = $this->getMockBuilder('OCA\Encryption\Util')
+			->disableOriginalConstructor()->getMock();
+		$this->keyManager = $this->getMockBuilder('OCA\Encryption\KeyManager')
+			->disableOriginalConstructor()->getMock();
+		$this->crypt = $this->getMockBuilder('OCA\Encryption\Crypto\Crypt')
+			->disableOriginalConstructor()->getMock();
+		$this->session = $this->getMockBuilder('OCA\Encryption\Session')
+			->disableOriginalConstructor()->getMock();
+		$this->questionHelper = $this->getMockBuilder('Symfony\Component\Console\Helper\QuestionHelper')
+			->disableOriginalConstructor()->getMock();
+
+		$this->instance = new DecryptAll(
+			$this->util,
+			$this->keyManager,
+			$this->crypt,
+			$this->session,
+			$this->questionHelper
+		);
+	}
+
+	public function testUpdateSession() {
+		$this->session->expects($this->once())->method('prepareDecryptAll')
+			->with('user1', 'key1');
+
+		$this->invokePrivate($this->instance, 'updateSession', ['user1', 'key1']);
+	}
+
+	/**
+	 * @dataProvider dataTestGetPrivateKey
+	 *
+	 * @param string $user
+	 * @param string $recoveryKeyId
+	 */
+	public function testGetPrivateKey($user, $recoveryKeyId) {
+		$password = 'passwd';
+		$recoveryKey = 'recoveryKey';
+		$userKey = 'userKey';
+		$unencryptedKey = 'unencryptedKey';
+
+		$this->keyManager->expects($this->any())->method('getRecoveryKeyId')
+			->willReturn($recoveryKeyId);
+
+		if ($user === $recoveryKeyId) {
+			$this->keyManager->expects($this->once())->method('getSystemPrivateKey')
+				->with($recoveryKeyId)->willReturn($recoveryKey);
+			$this->keyManager->expects($this->never())->method('getPrivateKey');
+			$this->crypt->expects($this->once())->method('decryptPrivateKey')
+				->with($recoveryKey, $password)->willReturn($unencryptedKey);
+		} else {
+			$this->keyManager->expects($this->never())->method('getSystemPrivateKey');
+			$this->keyManager->expects($this->once())->method('getPrivateKey')
+				->with($user)->willReturn($userKey);
+			$this->crypt->expects($this->once())->method('decryptPrivateKey')
+				->with($userKey, $password, $user)->willReturn($unencryptedKey);
+		}
+
+		$this->assertSame($unencryptedKey,
+			$this->invokePrivate($this->instance, 'getPrivateKey', [$user, $password])
+		);
+	}
+
+	public function dataTestGetPrivateKey() {
+		return [
+			['user1', 'recoveryKey'],
+			['recoveryKeyId', 'recoveryKeyId']
+		];
+	}
+
+}
diff --git a/apps/encryption/tests/lib/crypto/encryptionTest.php b/apps/encryption/tests/lib/crypto/encryptionTest.php
index f58aa5d3cc..9e0cb2f09d 100644
--- a/apps/encryption/tests/lib/crypto/encryptionTest.php
+++ b/apps/encryption/tests/lib/crypto/encryptionTest.php
@@ -39,6 +39,12 @@ class EncryptionTest extends TestCase {
 	/** @var \PHPUnit_Framework_MockObject_MockObject */
 	private $encryptAllMock;
 
+	/** @var \PHPUnit_Framework_MockObject_MockObject */
+	private $decryptAllMock;
+
+	/** @var \PHPUnit_Framework_MockObject_MockObject */
+	private $sessionMock;
+
 	/** @var \PHPUnit_Framework_MockObject_MockObject */
 	private $cryptMock;
 
@@ -63,9 +69,15 @@ class EncryptionTest extends TestCase {
 		$this->keyManagerMock = $this->getMockBuilder('OCA\Encryption\KeyManager')
 			->disableOriginalConstructor()
 			->getMock();
+		$this->sessionMock = $this->getMockBuilder('OCA\Encryption\Session')
+			->disableOriginalConstructor()
+			->getMock();
 		$this->encryptAllMock = $this->getMockBuilder('OCA\Encryption\Crypto\EncryptAll')
 			->disableOriginalConstructor()
 			->getMock();
+		$this->decryptAllMock = $this->getMockBuilder('OCA\Encryption\Crypto\DecryptAll')
+			->disableOriginalConstructor()
+			->getMock();
 		$this->loggerMock = $this->getMockBuilder('OCP\ILogger')
 			->disableOriginalConstructor()
 			->getMock();
@@ -81,7 +93,9 @@ class EncryptionTest extends TestCase {
 			$this->cryptMock,
 			$this->keyManagerMock,
 			$this->utilMock,
+			$this->sessionMock,
 			$this->encryptAllMock,
+			$this->decryptAllMock,
 			$this->loggerMock,
 			$this->l10nMock
 		);
@@ -170,6 +184,16 @@ class EncryptionTest extends TestCase {
 	 */
 	public function testBegin($mode, $header, $legacyCipher, $defaultCipher, $fileKey, $expected) {
 
+		$this->sessionMock->expects($this->once())
+			->method('decryptAllModeActivated')
+			->willReturn(false);
+
+		$this->sessionMock->expects($this->never())->method('getDecryptAllUid');
+		$this->sessionMock->expects($this->never())->method('getDecryptAllKey');
+		$this->keyManagerMock->expects($this->never())->method('getEncryptedFileKey');
+		$this->keyManagerMock->expects($this->never())->method('getShareKey');
+		$this->cryptMock->expects($this->never())->method('multiKeyDecrypt');
+
 		$this->cryptMock->expects($this->any())
 			->method('getCipher')
 			->willReturn($defaultCipher);
@@ -209,6 +233,49 @@ class EncryptionTest extends TestCase {
 		);
 	}
 
+
+	/**
+	 * test begin() if decryptAll mode was activated
+	 */
+	public function testBeginDecryptAll() {
+
+		$path = '/user/files/foo.txt';
+		$recoveryKeyId = 'recoveryKeyId';
+		$recoveryShareKey = 'recoveryShareKey';
+		$decryptAllKey = 'decryptAllKey';
+		$fileKey = 'fileKey';
+
+		$this->sessionMock->expects($this->once())
+			->method('decryptAllModeActivated')
+			->willReturn(true);
+		$this->sessionMock->expects($this->once())
+			->method('getDecryptAllUid')
+			->willReturn($recoveryKeyId);
+		$this->sessionMock->expects($this->once())
+			->method('getDecryptAllKey')
+			->willReturn($decryptAllKey);
+
+		$this->keyManagerMock->expects($this->once())
+			->method('getEncryptedFileKey')
+			->willReturn('encryptedFileKey');
+		$this->keyManagerMock->expects($this->once())
+			->method('getShareKey')
+			->with($path, $recoveryKeyId)
+			->willReturn($recoveryShareKey);
+		$this->cryptMock->expects($this->once())
+			->method('multiKeyDecrypt')
+			->with('encryptedFileKey', $recoveryShareKey, $decryptAllKey)
+			->willReturn($fileKey);
+
+		$this->keyManagerMock->expects($this->never())->method('getFileKey');
+
+		$this->instance->begin($path, 'user', 'r', [], []);
+
+		$this->assertSame($fileKey,
+			$this->invokePrivate($this->instance, 'fileKey')
+		);
+	}
+
 	/**
 	 * @dataProvider dataTestUpdate
 	 *
@@ -273,4 +340,15 @@ class EncryptionTest extends TestCase {
 	public function testDecrypt() {
 		$this->instance->decrypt('abc');
 	}
+
+	public function testPrepareDecryptAll() {
+		$input = $this->getMock('Symfony\Component\Console\Input\InputInterface');
+		$output = $this->getMock('Symfony\Component\Console\Output\OutputInterface');
+
+		$this->decryptAllMock->expects($this->once())->method('prepare')
+			->with($input, $output, 'user');
+
+		$this->instance->prepareDecryptAll($input, $output, 'user');
+	}
+
 }
diff --git a/core/command/encryption/decryptall.php b/core/command/encryption/decryptall.php
new file mode 100644
index 0000000000..374f635725
--- /dev/null
+++ b/core/command/encryption/decryptall.php
@@ -0,0 +1,148 @@
+<?php
+/**
+ * @author Björn Schießle <schiessle@owncloud.com>
+ *
+ * @copyright Copyright (c) 2015, ownCloud, Inc.
+ * @license AGPL-3.0
+ *
+ * This code is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License, version 3,
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ */
+
+namespace OC\Core\Command\Encryption;
+
+use OCP\App\IAppManager;
+use OCP\Encryption\IManager;
+use OCP\IConfig;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Helper\QuestionHelper;
+use Symfony\Component\Console\Input\InputArgument;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Output\OutputInterface;
+use Symfony\Component\Console\Question\ConfirmationQuestion;
+
+class DecryptAll extends Command {
+
+	/** @var IManager */
+	protected $encryptionManager;
+
+	/** @var  IAppManager */
+	protected $appManager;
+
+	/** @var IConfig */
+	protected $config;
+
+	/** @var  QuestionHelper */
+	protected $questionHelper;
+
+	/** @var bool */
+	protected $wasTrashbinEnabled;
+
+	/** @var  bool */
+	protected $wasSingleUserModeEnabled;
+
+	/** @var \OC\Encryption\DecryptAll */
+	protected $decryptAll;
+
+	/**
+	 * @param IManager $encryptionManager
+	 * @param IAppManager $appManager
+	 * @param IConfig $config
+	 * @param \OC\Encryption\DecryptAll $decryptAll
+	 * @param QuestionHelper $questionHelper
+	 */
+	public function __construct(
+		IManager $encryptionManager,
+		IAppManager $appManager,
+		IConfig $config,
+		\OC\Encryption\DecryptAll $decryptAll,
+		QuestionHelper $questionHelper
+	) {
+		parent::__construct();
+
+		$this->appManager = $appManager;
+		$this->encryptionManager = $encryptionManager;
+		$this->config = $config;
+		$this->decryptAll = $decryptAll;
+		$this->questionHelper = $questionHelper;
+
+		$this->wasTrashbinEnabled = $this->appManager->isEnabledForUser('files_trashbin');
+		$this->wasSingleUserModeEnabled = $this->config->getSystemValue('singleUser', false);
+		$this->config->setSystemValue('singleUser', true);
+		$this->appManager->disableApp('files_trashbin');
+	}
+
+	public function __destruct() {
+		$this->config->setSystemValue('singleUser', $this->wasSingleUserModeEnabled);
+		if ($this->wasTrashbinEnabled) {
+			$this->appManager->enableApp('files_trashbin');
+		}
+	}
+
+	protected function configure() {
+		parent::configure();
+
+		$this->setName('encryption:decrypt-all');
+		$this->setDescription(
+			'This will disable server-side encryption and decrypt all files for '
+			. 'all users if it is supported by your encryption module. '
+			. 'Please make sure that no user access his files during this process!'
+		);
+		$this->addArgument(
+			'user',
+			InputArgument::OPTIONAL,
+			'user for which you want to decrypt all files (optional)'
+		);
+	}
+
+	protected function execute(InputInterface $input, OutputInterface $output) {
+
+		try {
+			if ($this->encryptionManager->isEnabled() === true) {
+				$output->write('Disable server side encryption... ');
+				$this->config->setAppValue('core', 'encryption_enabled', 'no');
+				$output->writeln('done.');
+			} else {
+				$output->writeln('Server side encryption not enabled. Nothing to do.');
+				return;
+
+			}
+
+			$output->writeln("\n");
+			$output->writeln('You are about to start to decrypt all files stored in your ownCloud.');
+			$output->writeln('It will depend on the encryption module and your setup if this is possible.');
+			$output->writeln('Depending on the number and size of your files this can take some time');
+			$output->writeln('Please make sure that no user access his files during this process!');
+			$output->writeln('');
+			$question = new ConfirmationQuestion('Do you really want to continue? (y/n) ', false);
+			if ($this->questionHelper->ask($input, $output, $question)) {
+				$user = $input->getArgument('user');
+				$result = $this->decryptAll->decryptAll($input, $output, $user);
+				if ($result === false) {
+					$this->output->writeln(' aborted.');
+					$this->config->setAppValue('core', 'encryption_enabled', 'yes');
+				}
+			} else {
+				$output->write('Enable server side encryption... ');
+				$this->config->setAppValue('core', 'encryption_enabled', 'yes');
+				$output->writeln('done.');
+				$output->writeln('aborted');
+			}
+		} catch (\Exception $e) {
+			// enable server side encryption again if something went wrong
+			$this->config->setAppValue('core', 'encryption_enabled', 'yes');
+			throw $e;
+		}
+	}
+
+}
diff --git a/core/register_command.php b/core/register_command.php
index d3c04ad067..114e115c49 100644
--- a/core/register_command.php
+++ b/core/register_command.php
@@ -58,6 +58,13 @@ if (\OC::$server->getConfig()->getSystemValue('installed', false)) {
 	$application->add(new OC\Core\Command\Encryption\SetDefaultModule(\OC::$server->getEncryptionManager()));
 	$application->add(new OC\Core\Command\Encryption\Status(\OC::$server->getEncryptionManager()));
 	$application->add(new OC\Core\Command\Encryption\EncryptAll(\OC::$server->getEncryptionManager(), \OC::$server->getAppManager(), \OC::$server->getConfig(), new \Symfony\Component\Console\Helper\QuestionHelper()));
+	$application->add(new OC\Core\Command\Encryption\DecryptAll(
+		\OC::$server->getEncryptionManager(),
+		\OC::$server->getAppManager(),
+		\OC::$server->getConfig(),
+		new \OC\Encryption\DecryptAll(\OC::$server->getEncryptionManager(), \OC::$server->getUserManager(), new \OC\Files\View()),
+		new \Symfony\Component\Console\Helper\QuestionHelper())
+	);
 
 	$application->add(new OC\Core\Command\Log\Manage(\OC::$server->getConfig()));
 	$application->add(new OC\Core\Command\Log\OwnCloud(\OC::$server->getConfig()));
diff --git a/lib/private/encryption/decryptall.php b/lib/private/encryption/decryptall.php
new file mode 100644
index 0000000000..e59be17886
--- /dev/null
+++ b/lib/private/encryption/decryptall.php
@@ -0,0 +1,268 @@
+<?php
+/**
+ * @author Björn Schießle <schiessle@owncloud.com>
+ *
+ * @copyright Copyright (c) 2015, ownCloud, Inc.
+ * @license AGPL-3.0
+ *
+ * This code is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License, version 3,
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ */
+
+
+namespace OC\Encryption;
+
+use OC\Encryption\Exceptions\DecryptionFailedException;
+use OC\Files\View;
+use \OCP\Encryption\IEncryptionModule;
+use OCP\IUserManager;
+use Symfony\Component\Console\Helper\ProgressBar;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Output\OutputInterface;
+
+class DecryptAll {
+
+	/** @var  OutputInterface */
+	protected $output;
+
+	/** @var  InputInterface */
+	protected $input;
+
+	/** @var  Manager */
+	protected $encryptionManager;
+
+	/** @var IUserManager */
+	protected $userManager;
+
+	/** @var View */
+	protected $rootView;
+
+	/** @var  array files which couldn't be decrypted */
+	protected $failed;
+
+	/**
+	 * @param Manager $encryptionManager
+	 * @param IUserManager $userManager
+	 * @param View $rootView
+	 */
+	public function __construct(
+		Manager $encryptionManager,
+		IUserManager $userManager,
+		View $rootView
+	) {
+		$this->encryptionManager = $encryptionManager;
+		$this->userManager = $userManager;
+		$this->rootView = $rootView;
+		$this->failed = [];
+	}
+
+	/**
+	 * start to decrypt all files
+	 *
+	 * @param InputInterface $input
+	 * @param OutputInterface $output
+	 * @param string $user which users data folder should be decrypted, default = all users
+	 * @return bool
+	 * @throws \Exception
+	 */
+	public function decryptAll(InputInterface $input, OutputInterface $output, $user = '') {
+
+		$this->input = $input;
+		$this->output = $output;
+
+		$this->output->writeln('prepare encryption modules...');
+		if ($this->prepareEncryptionModules($user) === false) {
+			return false;
+		}
+		$this->output->writeln(' done.');
+
+		$this->decryptAllUsersFiles($user);
+
+		if (empty($this->failed)) {
+			$this->output->writeln('all files could be decrypted successfully!');
+		} else {
+			$this->output->writeln('Files for following users couldn\'t be decrypted, ');
+			$this->output->writeln('maybe the user is not set up in a way that supports this operation: ');
+			foreach ($this->failed as $uid => $paths) {
+				$this->output->writeln('    ' . $uid);
+			}
+			$this->output->writeln('');
+		}
+
+		return true;
+	}
+
+	/**
+	 * prepare encryption modules to perform the decrypt all function
+	 *
+	 * @param $user
+	 * @return bool
+	 */
+	protected function prepareEncryptionModules($user) {
+		// prepare all encryption modules for decrypt all
+		$encryptionModules = $this->encryptionManager->getEncryptionModules();
+		foreach ($encryptionModules as $moduleDesc) {
+			/** @var IEncryptionModule $module */
+			$module = call_user_func($moduleDesc['callback']);
+			if ($module->prepareDecryptAll($this->input, $this->output, $user) === false) {
+				$this->output->writeln('Module "' . $moduleDesc['displayName'] . '" does not support the functionality to decrypt all files again or the initialization of the module failed!');
+				return false;
+			}
+		}
+
+		return true;
+	}
+
+	/**
+	 * iterate over all user and encrypt their files
+	 * @param string $user which users files should be decrypted, default = all users
+	 */
+	protected function decryptAllUsersFiles($user = '') {
+
+		$this->output->writeln("\n");
+
+		$userList = [];
+		if (empty($user)) {
+
+			$fetchUsersProgress = new ProgressBar($this->output);
+			$fetchUsersProgress->setFormat(" %message% \n [%bar%]");
+			$fetchUsersProgress->start();
+			$fetchUsersProgress->setMessage("Fetch list of users...");
+			$fetchUsersProgress->advance();
+
+			foreach ($this->userManager->getBackends() as $backend) {
+				$limit = 500;
+				$offset = 0;
+				do {
+					$users = $backend->getUsers('', $limit, $offset);
+					foreach ($users as $user) {
+						$userList[] = $user;
+					}
+					$offset += $limit;
+					$fetchUsersProgress->advance();
+				} while (count($users) >= $limit);
+				$fetchUsersProgress->setMessage("Fetch list of users... finished");
+				$fetchUsersProgress->finish();
+			}
+		} else {
+			$userList[] = $user;
+		}
+
+		$this->output->writeln("\n\n");
+
+		$progress = new ProgressBar($this->output);
+		$progress->setFormat(" %message% \n [%bar%]");
+		$progress->start();
+		$progress->setMessage("starting to decrypt files...");
+		$progress->advance();
+
+		$numberOfUsers = count($userList);
+		$userNo = 1;
+		foreach ($userList as $uid) {
+			$userCount = "$uid ($userNo of $numberOfUsers)";
+			$this->decryptUsersFiles($uid, $progress, $userCount);
+			$userNo++;
+		}
+
+		$progress->setMessage("starting to decrypt files... finished");
+		$progress->finish();
+
+		$this->output->writeln("\n\n");
+
+	}
+
+	/**
+	 * encrypt files from the given user
+	 *
+	 * @param string $uid
+	 * @param ProgressBar $progress
+	 * @param string $userCount
+	 */
+	protected function decryptUsersFiles($uid, ProgressBar $progress, $userCount) {
+
+		$this->setupUserFS($uid);
+		$directories = array();
+		$directories[] =  '/' . $uid . '/files';
+
+		while($root = array_pop($directories)) {
+			$content = $this->rootView->getDirectoryContent($root);
+			foreach ($content as $file) {
+				$path = $root . '/' . $file['name'];
+				if ($this->rootView->is_dir($path)) {
+					$directories[] = $path;
+					continue;
+				} else {
+					try {
+						$progress->setMessage("decrypt files for user $userCount: $path");
+						$progress->advance();
+						if ($this->decryptFile($path) === false) {
+							$progress->setMessage("decrypt files for user $userCount: $path (already decrypted)");
+							$progress->advance();
+						}
+					} catch (\Exception $e) {
+						if (isset($this->failed[$uid])) {
+							$this->failed[$uid][] = $path;
+						} else {
+							$this->failed[$uid] = [$path];
+						}
+					}
+				}
+			}
+		}
+	}
+
+	/**
+	 * encrypt file
+	 *
+	 * @param string $path
+	 * @return bool
+	 */
+	protected function decryptFile($path) {
+
+		$source = $path;
+		$target = $path . '.decrypted.' . $this->getTimestamp();
+
+		try {
+			$this->rootView->copy($source, $target);
+			$this->rootView->rename($target, $source);
+		} catch (DecryptionFailedException $e) {
+			if ($this->rootView->file_exists($target)) {
+				$this->rootView->unlink($target);
+			}
+			return false;
+		}
+
+		return true;
+	}
+
+	/**
+	 * get current timestamp
+	 *
+	 * @return int
+	 */
+	protected function getTimestamp() {
+		return time();
+	}
+
+
+	/**
+	 * setup user file system
+	 *
+	 * @param string $uid
+	 */
+	protected function setupUserFS($uid) {
+		\OC_Util::tearDownFS();
+		\OC_Util::setupFS($uid);
+	}
+
+}
diff --git a/lib/public/encryption/iencryptionmodule.php b/lib/public/encryption/iencryptionmodule.php
index 0fa0dc570d..66cf1a80e0 100644
--- a/lib/public/encryption/iencryptionmodule.php
+++ b/lib/public/encryption/iencryptionmodule.php
@@ -145,4 +145,15 @@ interface IEncryptionModule {
 	 */
 	public function encryptAll(InputInterface $input, OutputInterface $output);
 
+	/**
+	 * prepare encryption module to decrypt all files
+	 *
+	 * @param InputInterface $input
+	 * @param OutputInterface $output write some status information to the terminal during encryption
+	 * @param $user (optional) for which the files should be decrypted, default = all users
+	 * @return bool return false on failure or if it isn't supported by the module
+	 * @since 8.2.0
+	 */
+	public function prepareDecryptAll(InputInterface $input, OutputInterface $output, $user = '');
+
 }
diff --git a/tests/core/command/encryption/decryptalltest.php b/tests/core/command/encryption/decryptalltest.php
new file mode 100644
index 0000000000..b7fd630e9b
--- /dev/null
+++ b/tests/core/command/encryption/decryptalltest.php
@@ -0,0 +1,215 @@
+<?php
+/**
+ * @author Björn Schießle <schiessle@owncloud.com>
+ *
+ * @copyright Copyright (c) 2015, ownCloud, Inc.
+ * @license AGPL-3.0
+ *
+ * This code is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License, version 3,
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ */
+
+
+namespace Tests\Core\Command\Encryption;
+
+
+use OC\Core\Command\Encryption\DecryptAll;
+use Test\TestCase;
+
+class DecryptAllTest extends TestCase {
+
+	/** @var \PHPUnit_Framework_MockObject_MockObject | \OCP\IConfig */
+	protected $config;
+
+	/** @var \PHPUnit_Framework_MockObject_MockObject | \OCP\Encryption\IManager  */
+	protected $encryptionManager;
+
+	/** @var \PHPUnit_Framework_MockObject_MockObject | \OCP\App\IAppManager  */
+	protected $appManager;
+
+	/** @var \PHPUnit_Framework_MockObject_MockObject  | \Symfony\Component\Console\Input\InputInterface */
+	protected $consoleInput;
+
+	/** @var \PHPUnit_Framework_MockObject_MockObject | \Symfony\Component\Console\Output\OutputInterface */
+	protected $consoleOutput;
+
+	/** @var \PHPUnit_Framework_MockObject_MockObject | \Symfony\Component\Console\Helper\QuestionHelper */
+	protected $questionHelper;
+
+	/** @var \PHPUnit_Framework_MockObject_MockObject | \OC\Encryption\DecryptAll */
+	protected $decryptAll;
+
+	public function setUp() {
+		parent::setUp();
+
+		$this->config = $this->getMockBuilder('OCP\IConfig')
+			->disableOriginalConstructor()
+			->getMock();
+		$this->encryptionManager = $this->getMockBuilder('OCP\Encryption\IManager')
+			->disableOriginalConstructor()
+			->getMock();
+		$this->appManager = $this->getMockBuilder('OCP\App\IAppManager')
+			->disableOriginalConstructor()
+			->getMock();
+		$this->questionHelper = $this->getMockBuilder('Symfony\Component\Console\Helper\QuestionHelper')
+			->disableOriginalConstructor()
+			->getMock();
+		$this->decryptAll = $this->getMockBuilder('OC\Encryption\DecryptAll')
+			->disableOriginalConstructor()->getMock();
+		$this->consoleInput = $this->getMock('Symfony\Component\Console\Input\InputInterface');
+		$this->consoleOutput = $this->getMock('Symfony\Component\Console\Output\OutputInterface');
+
+		$this->config->expects($this->any())
+			->method('getSystemValue')
+			->with('singleUser', false)
+			->willReturn(false);
+		$this->appManager->expects($this->any())
+			->method('isEnabledForUser')
+			->with('files_trashbin')->willReturn(true);
+
+	}
+
+	public function testConstructDesctruct() {
+		// on construct we enable single-user-mode and disable the trash bin
+		$this->config->expects($this->at(1))
+			->method('setSystemValue')
+			->with('singleUser', true);
+		$this->appManager->expects($this->once())
+			->method('disableApp')
+			->with('files_trashbin');
+
+		// on destruct wi disable single-user-mode again and enable the trash bin
+		$this->config->expects($this->at(2))
+			->method('setSystemValue')
+			->with('singleUser', false);
+		$this->appManager->expects($this->once())
+			->method('enableApp')
+			->with('files_trashbin');
+
+		$instance = new DecryptAll(
+			$this->encryptionManager,
+			$this->appManager,
+			$this->config,
+			$this->decryptAll,
+			$this->questionHelper
+		);
+
+		$this->assertTrue(
+			$this->invokePrivate($instance, 'wasTrashbinEnabled')
+		);
+
+		$this->assertFalse(
+			$this->invokePrivate($instance, 'wasSingleUserModeEnabled')
+		);
+	}
+
+	/**
+	 * @dataProvider dataTestExecute
+	 */
+	public function testExecute($encryptionEnabled, $continue) {
+
+		$instance = new DecryptAll(
+			$this->encryptionManager,
+			$this->appManager,
+			$this->config,
+			$this->decryptAll,
+			$this->questionHelper
+		);
+
+		$this->encryptionManager->expects($this->once())
+			->method('isEnabled')
+			->willReturn($encryptionEnabled);
+
+		$this->consoleInput->expects($this->any())
+			->method('getArgument')
+			->with('user')
+			->willReturn('user1');
+
+		if ($encryptionEnabled) {
+			$this->config->expects($this->at(0))
+				->method('setAppValue')
+				->with('core', 'encryption_enabled', 'no');
+			$this->questionHelper->expects($this->once())
+				->method('ask')
+				->willReturn($continue);
+			if ($continue) {
+				$this->decryptAll->expects($this->once())
+					->method('decryptAll')
+					->with($this->consoleInput, $this->consoleOutput, 'user1');
+			} else {
+				$this->decryptAll->expects($this->never())->method('decryptAll');
+				$this->config->expects($this->at(1))
+					->method('setAppValue')
+					->with('core', 'encryption_enabled', 'yes');
+			}
+		} else {
+			$this->config->expects($this->never())->method('setAppValue');
+			$this->decryptAll->expects($this->never())->method('decryptAll');
+			$this->questionHelper->expects($this->never())->method('ask');
+		}
+
+		$this->invokePrivate($instance, 'execute', [$this->consoleInput, $this->consoleOutput]);
+	}
+
+	public function dataTestExecute() {
+		return [
+			[true, true],
+			[true, false],
+			[false, true],
+			[false, false]
+		];
+	}
+
+	/**
+	 * @expectedException \Exception
+	 */
+	public function testExecuteFailure() {
+		$instance = new DecryptAll(
+			$this->encryptionManager,
+			$this->appManager,
+			$this->config,
+			$this->decryptAll,
+			$this->questionHelper
+		);
+
+		$this->config->expects($this->at(0))
+			->method('setAppValue')
+			->with('core', 'encryption_enabled', 'no');
+
+		// make sure that we enable encryption again after a exception was thrown
+		$this->config->expects($this->at(1))
+			->method('setAppValue')
+			->with('core', 'encryption_enabled', 'yes');
+
+		$this->encryptionManager->expects($this->once())
+			->method('isEnabled')
+			->willReturn(true);
+
+		$this->consoleInput->expects($this->any())
+			->method('getArgument')
+			->with('user')
+			->willReturn('user1');
+
+		$this->questionHelper->expects($this->once())
+			->method('ask')
+			->willReturn(true);
+
+		$this->decryptAll->expects($this->once())
+			->method('decryptAll')
+			->with($this->consoleInput, $this->consoleOutput, 'user1')
+			->willReturnCallback(function() { throw new \Exception(); });
+
+		$this->invokePrivate($instance, 'execute', [$this->consoleInput, $this->consoleOutput]);
+	}
+
+}
diff --git a/tests/lib/encryption/decryptalltest.php b/tests/lib/encryption/decryptalltest.php
new file mode 100644
index 0000000000..eb3bc721f8
--- /dev/null
+++ b/tests/lib/encryption/decryptalltest.php
@@ -0,0 +1,321 @@
+<?php
+/**
+ * @author Björn Schießle <schiessle@owncloud.com>
+ *
+ * @copyright Copyright (c) 2015, ownCloud, Inc.
+ * @license AGPL-3.0
+ *
+ * This code is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License, version 3,
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ */
+
+
+namespace Test\Encryption;
+
+
+use OC\Encryption\DecryptAll;
+use OC\Encryption\Exceptions\DecryptionFailedException;
+use OC\Encryption\Manager;
+use OC\Files\View;
+use OCP\IUserManager;
+use Test\TestCase;
+
+class DecryptAllTest extends TestCase {
+
+	/** @var \PHPUnit_Framework_MockObject_MockObject | IUserManager */
+	protected $userManager;
+
+	/** @var \PHPUnit_Framework_MockObject_MockObject | Manager */
+	protected $encryptionManager;
+
+	/** @var \PHPUnit_Framework_MockObject_MockObject | View */
+	protected $view;
+
+	/** @var  \PHPUnit_Framework_MockObject_MockObject | \Symfony\Component\Console\Input\InputInterface */
+	protected $inputInterface;
+
+	/** @var  \PHPUnit_Framework_MockObject_MockObject | \Symfony\Component\Console\Output\OutputInterface */
+	protected $outputInterface;
+
+	/** @var  \PHPUnit_Framework_MockObject_MockObject | \OCP\UserInterface */
+	protected $userInterface;
+
+	/** @var  DecryptAll */
+	protected $instance;
+
+	public function setUp() {
+		parent::setUp();
+
+		$this->userManager = $this->getMockBuilder('OCP\IUserManager')
+			->disableOriginalConstructor()->getMock();
+		$this->encryptionManager = $this->getMockBuilder('OC\Encryption\Manager')
+			->disableOriginalConstructor()->getMock();
+		$this->view = $this->getMockBuilder('OC\Files\View')
+			->disableOriginalConstructor()->getMock();
+		$this->inputInterface = $this->getMockBuilder('Symfony\Component\Console\Input\InputInterface')
+			->disableOriginalConstructor()->getMock();
+		$this->outputInterface = $this->getMockBuilder('Symfony\Component\Console\Output\OutputInterface')
+			->disableOriginalConstructor()->getMock();
+		$this->userInterface = $this->getMockBuilder('OCP\UserInterface')
+			->disableOriginalConstructor()->getMock();
+
+		$this->outputInterface->expects($this->any())->method('getFormatter')
+			->willReturn($this->getMock('\Symfony\Component\Console\Formatter\OutputFormatterInterface'));
+
+		$this->instance = new DecryptAll($this->encryptionManager, $this->userManager, $this->view);
+
+		$this->invokePrivate($this->instance, 'input', [$this->inputInterface]);
+		$this->invokePrivate($this->instance, 'output', [$this->outputInterface]);
+	}
+
+	/**
+	 * @dataProvider dataTrueFalse
+	 */
+	public function testDecryptAll($prepareResult) {
+
+		$user = 'user1';
+
+		/** @var DecryptAll | \PHPUnit_Framework_MockObject_MockObject |  $instance */
+		$instance = $this->getMockBuilder('OC\Encryption\DecryptAll')
+			->setConstructorArgs(
+				[
+					$this->encryptionManager,
+					$this->userManager,
+					$this->view
+				]
+			)
+			->setMethods(['prepareEncryptionModules', 'decryptAllUsersFiles'])
+			->getMock();
+
+		$instance->expects($this->once())
+			->method('prepareEncryptionModules')
+			->with($user)
+			->willReturn($prepareResult);
+
+		if ($prepareResult) {
+			$instance->expects($this->once())
+				->method('decryptAllUsersFiles')
+				->with($user);
+		} else {
+			$instance->expects($this->never())->method('decryptAllUsersFiles');
+		}
+
+		$instance->decryptAll($this->inputInterface, $this->outputInterface, $user);
+	}
+
+	public function dataTrueFalse() {
+		return [
+			[true],
+			[false]
+		];
+	}
+
+	/**
+	 * @dataProvider dataTrueFalse
+	 */
+	public function testPrepareEncryptionModules($success) {
+
+		$user = 'user1';
+
+		$dummyEncryptionModule = $this->getMockBuilder('OCP\Encryption\IEncryptionModule')
+			->disableOriginalConstructor()->getMock();
+
+		$dummyEncryptionModule->expects($this->once())
+			->method('prepareDecryptAll')
+			->with($this->inputInterface, $this->outputInterface, $user)
+			->willReturn($success);
+
+		$callback = function() use ($dummyEncryptionModule) {return $dummyEncryptionModule;};
+		$moduleDescription = [
+			'id' => 'id',
+			'displayName' => 'displayName',
+			'callback' => $callback
+		];
+
+		$this->encryptionManager->expects($this->once())
+			->method('getEncryptionModules')
+			->willReturn([$moduleDescription]);
+
+		$this->assertSame($success,
+			$this->invokePrivate($this->instance, 'prepareEncryptionModules', [$user])
+		);
+	}
+
+	/**
+	 * @dataProvider dataTestDecryptAllUsersFiles
+	 */
+	public function testDecryptAllUsersFiles($user) {
+
+		/** @var DecryptAll | \PHPUnit_Framework_MockObject_MockObject |  $instance */
+		$instance = $this->getMockBuilder('OC\Encryption\DecryptAll')
+			->setConstructorArgs(
+				[
+					$this->encryptionManager,
+					$this->userManager,
+					$this->view
+				]
+			)
+			->setMethods(['decryptUsersFiles'])
+			->getMock();
+
+		$this->invokePrivate($instance, 'input', [$this->inputInterface]);
+		$this->invokePrivate($instance, 'output', [$this->outputInterface]);
+
+		if (empty($user)) {
+			$this->userManager->expects($this->once())
+				->method('getBackends')
+				->willReturn([$this->userInterface]);
+			$this->userInterface->expects($this->any())
+				->method('getUsers')
+				->willReturn(['user1', 'user2']);
+			$instance->expects($this->at(0))
+				->method('decryptUsersFiles')
+				->with('user1');
+			$instance->expects($this->at(1))
+				->method('decryptUsersFiles')
+				->with('user2');
+		} else {
+			$instance->expects($this->once())
+				->method('decryptUsersFiles')
+				->with($user);
+		}
+
+		$this->invokePrivate($instance, 'decryptAllUsersFiles', [$user]);
+	}
+
+	public function dataTestDecryptAllUsersFiles() {
+		return [
+			['user1'],
+			['']
+		];
+	}
+
+	public function testDecryptUsersFiles() {
+		/** @var DecryptAll | \PHPUnit_Framework_MockObject_MockObject  $instance */
+		$instance = $this->getMockBuilder('OC\Encryption\DecryptAll')
+			->setConstructorArgs(
+				[
+					$this->encryptionManager,
+					$this->userManager,
+					$this->view
+				]
+			)
+			->setMethods(['decryptFile'])
+			->getMock();
+
+		$this->view->expects($this->at(0))->method('getDirectoryContent')
+			->with('/user1/files')->willReturn(
+				[
+					['name' => 'foo', 'type'=>'dir'],
+					['name' => 'bar', 'type'=>'file'],
+				]
+			);
+
+		$this->view->expects($this->at(3))->method('getDirectoryContent')
+			->with('/user1/files/foo')->willReturn(
+				[
+					['name' => 'subfile', 'type'=>'file']
+				]
+			);
+
+		$this->view->expects($this->any())->method('is_dir')
+			->willReturnCallback(
+				function($path) {
+					if ($path === '/user1/files/foo') {
+						return true;
+					}
+					return false;
+				}
+			);
+
+		$instance->expects($this->at(0))
+			->method('decryptFile')
+			->with('/user1/files/bar');
+		$instance->expects($this->at(1))
+			->method('decryptFile')
+			->with('/user1/files/foo/subfile');
+
+		$progressBar = $this->getMockBuilder('Symfony\Component\Console\Helper\ProgressBar')
+			->disableOriginalConstructor()->getMock();
+
+		$this->invokePrivate($instance, 'decryptUsersFiles', ['user1', $progressBar, '']);
+
+	}
+
+	public function testDecryptFile() {
+
+		$path = 'test.txt';
+
+		/** @var DecryptAll | \PHPUnit_Framework_MockObject_MockObject  $instance */
+		$instance = $this->getMockBuilder('OC\Encryption\DecryptAll')
+			->setConstructorArgs(
+				[
+					$this->encryptionManager,
+					$this->userManager,
+					$this->view
+				]
+			)
+			->setMethods(['getTimestamp'])
+			->getMock();
+
+		$instance->expects($this->any())->method('getTimestamp')->willReturn(42);
+
+		$this->view->expects($this->once())
+			->method('copy')
+			->with($path, $path . '.decrypted.42');
+		$this->view->expects($this->once())
+			->method('rename')
+			->with($path . '.decrypted.42', $path);
+
+		$this->assertTrue(
+			$this->invokePrivate($instance, 'decryptFile', [$path])
+		);
+	}
+
+	public function testDecryptFileFailure() {
+		$path = 'test.txt';
+
+		/** @var DecryptAll | \PHPUnit_Framework_MockObject_MockObject  $instance */
+		$instance = $this->getMockBuilder('OC\Encryption\DecryptAll')
+			->setConstructorArgs(
+				[
+					$this->encryptionManager,
+					$this->userManager,
+					$this->view
+				]
+			)
+			->setMethods(['getTimestamp'])
+			->getMock();
+
+		$instance->expects($this->any())->method('getTimestamp')->willReturn(42);
+
+		$this->view->expects($this->once())
+			->method('copy')
+			->with($path, $path . '.decrypted.42')
+			->willReturnCallback(function() { throw new DecryptionFailedException();});
+
+		$this->view->expects($this->never())->method('rename');
+		$this->view->expects($this->once())
+			->method('file_exists')
+			->with($path . '.decrypted.42')
+			->willReturn(true);
+		$this->view->expects($this->once())
+			->method('unlink')
+			->with($path . '.decrypted.42');
+
+		$this->assertFalse(
+			$this->invokePrivate($instance, 'decryptFile', [$path])
+		);
+	}
+
+}
diff --git a/tests/lib/files/storage/wrapper/encryption.php b/tests/lib/files/storage/wrapper/encryption.php
index 36a5b288c6..44e910b901 100644
--- a/tests/lib/files/storage/wrapper/encryption.php
+++ b/tests/lib/files/storage/wrapper/encryption.php
@@ -194,7 +194,7 @@ class Encryption extends \Test\Files\Storage\Storage {
 	protected function buildMockModule() {
 		$this->encryptionModule = $this->getMockBuilder('\OCP\Encryption\IEncryptionModule')
 			->disableOriginalConstructor()
-			->setMethods(['getId', 'getDisplayName', 'begin', 'end', 'encrypt', 'decrypt', 'update', 'shouldEncrypt', 'getUnencryptedBlockSize', 'isReadable', 'encryptAll'])
+			->setMethods(['getId', 'getDisplayName', 'begin', 'end', 'encrypt', 'decrypt', 'update', 'shouldEncrypt', 'getUnencryptedBlockSize', 'isReadable', 'encryptAll', 'prepareDecryptAll'])
 			->getMock();
 
 		$this->encryptionModule->expects($this->any())->method('getId')->willReturn('UNIT_TEST_MODULE');
diff --git a/tests/lib/files/stream/encryption.php b/tests/lib/files/stream/encryption.php
index ed3b5b1b15..f9d8f076b6 100644
--- a/tests/lib/files/stream/encryption.php
+++ b/tests/lib/files/stream/encryption.php
@@ -305,7 +305,7 @@ class Encryption extends \Test\TestCase {
 	protected function buildMockModule() {
 		$encryptionModule = $this->getMockBuilder('\OCP\Encryption\IEncryptionModule')
 			->disableOriginalConstructor()
-			->setMethods(['getId', 'getDisplayName', 'begin', 'end', 'encrypt', 'decrypt', 'update', 'shouldEncrypt', 'getUnencryptedBlockSize', 'isReadable', 'encryptAll'])
+			->setMethods(['getId', 'getDisplayName', 'begin', 'end', 'encrypt', 'decrypt', 'update', 'shouldEncrypt', 'getUnencryptedBlockSize', 'isReadable', 'encryptAll', 'prepareDecryptAll'])
 			->getMock();
 
 		$encryptionModule->expects($this->any())->method('getId')->willReturn('UNIT_TEST_MODULE');