Large file encryption/decryption

doc/01-Formats.md

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+# Cryptographic Message Formats
+
+## `\Defuse\Crypto\Crypto`
+
+`[____HMAC____][____IV____][____CIPHERTEXT____]`
+
+## `\Defuse\Crypto\File`
+
+`[____FIRST_NONCE____][____CIPHERTEXT____][____HMAC____]`

doc/02-Crypto.php.md

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+Symmetric Key Encryption
+========================
+
+At a glance:
+
+* **Cipher and Mode**: `AES-128-CBC`
+* **Padding**: `PKCS#7`
+* **Authentication**: `HMAC-SHA-256`
+* **Construction**: `Encrypt then MAC`
+* **Algorithm Backend**: `ext/openssl`
+
+## `\Defuse\Crypto\Crypto`
+
+**WARNING:** This encryption library is not a silver bullet. It only provides
+symmetric encryption given a uniformly random key. This means you **MUST NOT**
+use an ASCII string like a password as the key parameter, it **MUST** be
+a uniformly random key generated by `createNewRandomKey()`. If you want to
+encrypt something with a password, apply a password key derivation function
+like PBKDF2 or scrypt with a random salt to generate a key.
+
+***WARNING:*** Error handling is *very* important, especially for crypto code! 
+
+How to use this code:
+=====================
+
+Generating a Key
+----------------
+
+```php
+try {
+    $key = \Defuse\Crypto\Crypto::createNewRandomKey();
+    // WARNING: Do NOT encode $key with bin2hex() or base64_encode(),
+    // they may leak the key to the attacker through side channels.
+    // 
+    // This library offers these two for cache-timing-safe encoding:
+    //
+    //     \Defuse\Crypto\Crypto\binToHex()
+    //     \Defuse\Crypto\Crypto\hexToBin()
+    //
+} catch (\Defuse\Crypto\Exception\CryptoTestFailed $ex) {
+    die('Cannot safely create a key');
+} catch (\Defuse\Crypto\Exception\CannotPerformOperation $ex) {
+    die('Cannot safely create a key');
+}
+```
+
+Encrypting a Message
+--------------------
+
+```php
+$message = 'ATTACK AT DAWN';
+try {
+    $ciphertext = \Defuse\Crypto\Crypto::Encrypt($message, $key);
+} catch (\Defuse\Crypto\Exception\CryptoTestFailed $ex) {
+    die('Cannot safely perform encryption');
+} catch (\Defuse\Crypto\Exception\CannotPerformOperation $ex) {
+    die('Cannot safely perform encryption');
+}
+```
+
+Decrypting a Message
+--------------------
+
+```php
+try {
+    $decrypted = self::Decrypt($ciphertext, $key);
+} catch (\Defuse\Crypto\Exception\InvalidCiphertext $ex) { // VERY IMPORTANT
+    // Either:
+    //   1. The ciphertext was modified by the attacker,
+    //   2. The key is wrong, or
+    //   3. $ciphertext is not a valid ciphertext or was corrupted.
+    // Assume the worst.
+    die('DANGER! DANGER! The ciphertext has been tampered with!');
+} catch (CryptoTestFailedException $ex) {
+    die('Cannot safely perform decryption');
+} catch (CannotPerformOperationException $ex) {
+    die('Cannot safely perform decryption');
+}
+```

doc/03-File.php.md

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+Symmetric Key File Encryption
+=============================
+
+At a glance:
+
+* **Cipher and Mode**: `AES-128-CTR`
+* **Padding**: None (CTR mode doesn't pad)
+* **Authentication**: `HMAC-SHA-256`
+* **Construction**: `Encrypt then MAC`
+* **Algorithm Backend**: `ext/openssl`
+
+## `\Defuse\Crypto\File`
+
+**WARNING:** This encryption library is not a silver bullet. It only provides
+symmetric encryption given a uniformly random key. This means you **MUST NOT**
+use an ASCII string like a password as the key parameter, it **MUST** be
+a uniformly random key generated by `createNewRandomKey()`. If you want to
+encrypt something with a password, apply a password key derivation function
+like PBKDF2 or scrypt with a random salt to generate a key.
+
+***WARNING:*** Error handling is *very* important, especially for crypto code! 
+
+How to use this code:
+=====================
+
+Generating a Key
+----------------
+
+```php
+try {
+    $key = \Defuse\Crypto\File::createNewRandomKey();
+    // WARNING: Do NOT encode $key with bin2hex() or base64_encode(),
+    // they may leak the key to the attacker through side channels.
+    // 
+    // This library offers these two for cache-timing-safe encoding:
+    //
+    //     \Defuse\Crypto\File\binToHex()
+    //     \Defuse\Crypto\File\hexToBin()
+    //
+} catch (\Defuse\Crypto\Exception\CryptoTestFailed $ex) {
+    die('Cannot safely create a key');
+} catch (\Defuse\Crypto\Exception\CannotPerformOperation $ex) {
+    die('Cannot safely create a key');
+}
+
+Encrypting a File
+-----------------
+
+```php
+/* 
+  // Don't forget to generate a random key
+  $key = \Defuse\Crypto\File::createNewRandomKey();
+*/
+
+$inputFilename = 'image.jpg';
+$outputFilename = 'image.enc.jpg';
+
+try {
+    \Defuse\Crypto\File::encryptFile(
+        $inputFilename,
+        $outputFilename,
+        $key
+    );
+} catch (\Defuse\Crypto\Exception\CryptoTestFailed $ex) {
+    die('Cannot safely perform encryption');
+} catch (\Defuse\Crypto\Exception\CannotPerformOperation $ex) {
+    die('Cannot safely perform encryption');
+}
+```
+
+Decrypting a File
+-----------------
+
+```php
+/* 
+  // Don't forget to generate a random key
+  $key = \Defuse\Crypto\File::createNewRandomKey();
+*/
+
+$inputFilename = 'image.enc.jpg';
+$outputFilename = 'image.dec.jpg';
+
+try {
+    \Defuse\Crypto\File::decryptFile(
+        $inputFilename,
+        $outputFilename,
+        $key
+    );
+} catch (\Defuse\Crypto\Exception\CryptoTestFailed $ex) {
+    die('Cannot safely perform decryption');
+} catch (\Defuse\Crypto\Exception\CannotPerformOperation $ex) {
+    die('Cannot safely perform decryption');
+}
+```
+
+Encrypting a File Resource
+--------------------------
+
+```php
+/* 
+  // Don't forget to generate a random key
+  $key = \Defuse\Crypto\File::createNewRandomKey();
+*/
+
+$iFile = \fopen('image2.jpg', 'rb');
+$oFile = \fopen('image2.enc.jpg', 'wb');
+
+try {
+    \Defuse\Crypto\File::encryptResource($iFile, $oFile, $key);
+} catch (\Defuse\Crypto\Exception\CryptoTestFailed $ex) {
+    die('Cannot safely perform encryption');
+} catch (\Defuse\Crypto\Exception\CannotPerformOperation $ex) {
+    die('Cannot safely perform encryption');
+}
+```
+
+Decrypting a File Resource
+--------------------------
+
+```php
+/* 
+  // Don't forget to generate a random key
+  $key = \Defuse\Crypto\File::createNewRandomKey();
+*/
+
+$iFile = \fopen('image2.enc.jpg', 'rb');
+$oFile = \fopen('image2.dec.jpg', 'wb');
+
+try {
+    \Defuse\Crypto\File::decryptResource($iFile, $oFile, $key);
+} catch (\Defuse\Crypto\Exception\CryptoTestFailed $ex) {
+    die('Cannot safely perform decryption');
+} catch (\Defuse\Crypto\Exception\CannotPerformOperation $ex) {
+    die('Cannot safely perform decryption');
+}
+```

doc/README.md

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+# PHP Encryption Documentation
+
+Web: https://defuse.ca/secure-php-encryption.htm
+GitHub: https://github.com/defuse/php-encryption