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src/js/lib/cryptojs/mode-cfb.js

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+/*
+CryptoJS v3.1.2
+code.google.com/p/crypto-js
+(c) 2009-2013 by Jeff Mott. All rights reserved.
+code.google.com/p/crypto-js/wiki/License
+*/
+/**
+ * Cipher Feedback block mode.
+ */
+CryptoJS.mode.CFB = (function () {
+    var CFB = CryptoJS.lib.BlockCipherMode.extend();
+
+    CFB.Encryptor = CFB.extend({
+        processBlock: function (words, offset) {
+            // Shortcuts
+            var cipher = this._cipher;
+            var blockSize = cipher.blockSize;
+
+            generateKeystreamAndEncrypt.call(this, words, offset, blockSize, cipher);
+
+            // Remember this block to use with next block
+            this._prevBlock = words.slice(offset, offset + blockSize);
+        }
+    });
+
+    CFB.Decryptor = CFB.extend({
+        processBlock: function (words, offset) {
+            // Shortcuts
+            var cipher = this._cipher;
+            var blockSize = cipher.blockSize;
+
+            // Remember this block to use with next block
+            var thisBlock = words.slice(offset, offset + blockSize);
+
+            generateKeystreamAndEncrypt.call(this, words, offset, blockSize, cipher);
+
+            // This block becomes the previous block
+            this._prevBlock = thisBlock;
+        }
+    });
+
+    function generateKeystreamAndEncrypt(words, offset, blockSize, cipher) {
+        // Shortcut
+        var iv = this._iv;
+
+        // Generate keystream
+        if (iv) {
+            var keystream = iv.slice(0);
+
+            // Remove IV for subsequent blocks
+            this._iv = undefined;
+        } else {
+            var keystream = this._prevBlock;
+        }
+        cipher.encryptBlock(keystream, 0);
+
+        // Encrypt
+        for (var i = 0; i < blockSize; i++) {
+            words[offset + i] ^= keystream[i];
+        }
+    }
+
+    return CFB;
+}());