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<h1 class="page-title">Source: crypto/cfb.js</h1>
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<pre class="prettyprint source"><code>// Modified by Recurity Labs GmbH
// modified version of http://www.hanewin.net/encrypt/PGdecode.js:
/* OpenPGP encryption using RSA/AES
* Copyright 2005-2006 Herbert Hanewinkel, www.haneWIN.de
* version 2.0, check www.haneWIN.de for the latest version
* This software is provided as-is, without express or implied warranty.
* Permission to use, copy, modify, distribute or sell this software, with or
* without fee, for any purpose and by any individual or organization, is hereby
* granted, provided that the above copyright notice and this paragraph appear
* in all copies. Distribution as a part of an application or binary must
* include the above copyright notice in the documentation and/or other
* materials provided with the application or distribution.
*/
/**
* @requires crypto/cipher
* @requires util
* @module crypto/cfb
*/
var util = require('../util'),
cipher = require('./cipher');
module.exports = {
/**
* This function encrypts a given with the specified prefixrandom
* using the specified blockcipher to encrypt a message
* @param {String} prefixrandom random bytes of block_size length provided
* as a string to be used in prefixing the data
* @param {String} cipherfn the algorithm cipher class to encrypt
* data in one block_size encryption, {@link module:crypto/cipher}.
* @param {String} plaintext data to be encrypted provided as a string
* @param {String} key binary string representation of key to be used to encrypt the plaintext.
* This will be passed to the cipherfn
* @param {Boolean} resync a boolean value specifying if a resync of the
* IV should be used or not. The encrypteddatapacket uses the
* "old" style with a resync. Encryption within an
* encryptedintegrityprotecteddata packet is not resyncing the IV.
* @return {String} a string with the encrypted data
*/
encrypt: function(prefixrandom, cipherfn, plaintext, key, resync) {
cipherfn = new cipher[cipherfn](key);
var block_size = cipherfn.blockSize;
var FR = new Array(block_size);
var FRE = new Array(block_size);
prefixrandom = prefixrandom + prefixrandom.charAt(block_size - 2) + prefixrandom.charAt(block_size - 1);
util.print_debug("prefixrandom:" + util.hexstrdump(prefixrandom));
var ciphertext = "";
var i;
// 1. The feedback register (FR) is set to the IV, which is all zeros.
for (i = 0; i < block_size; i++) FR[i] = 0;
// 2. FR is encrypted to produce FRE (FR Encrypted). This is the
// encryption of an all-zero value.
FRE = cipherfn.encrypt(FR);
// 3. FRE is xored with the first BS octets of random data prefixed to
// the plaintext to produce C[1] through C[BS], the first BS octets
// of ciphertext.
for (i = 0; i < block_size; i++) ciphertext += String.fromCharCode(FRE[i] ^ prefixrandom.charCodeAt(i));
// 4. FR is loaded with C[1] through C[BS].
for (i = 0; i < block_size; i++) FR[i] = ciphertext.charCodeAt(i);
// 5. FR is encrypted to produce FRE, the encryption of the first BS
// octets of ciphertext.
FRE = cipherfn.encrypt(FR);
// 6. The left two octets of FRE get xored with the next two octets of
// data that were prefixed to the plaintext. This produces C[BS+1]
// and C[BS+2], the next two octets of ciphertext.
ciphertext += String.fromCharCode(FRE[0] ^ prefixrandom.charCodeAt(block_size));
ciphertext += String.fromCharCode(FRE[1] ^ prefixrandom.charCodeAt(block_size + 1));
if (resync) {
// 7. (The resync step) FR is loaded with C3-C10.
for (i = 0; i < block_size; i++) FR[i] = ciphertext.charCodeAt(i + 2);
} else {
for (i = 0; i < block_size; i++) FR[i] = ciphertext.charCodeAt(i);
}
// 8. FR is encrypted to produce FRE.
FRE = cipherfn.encrypt(FR, key);
if (resync) {
// 9. FRE is xored with the first 8 octets of the given plaintext, now
// that we have finished encrypting the 10 octets of prefixed data.
// This produces C11-C18, the next 8 octets of ciphertext.
for (i = 0; i < block_size; i++)
ciphertext += String.fromCharCode(FRE[i] ^ plaintext.charCodeAt(i));
for (n = block_size + 2; n < plaintext.length; n += block_size) {
// 10. FR is loaded with C11-C18
for (i = 0; i < block_size; i++) FR[i] = ciphertext.charCodeAt(n + i);
// 11. FR is encrypted to produce FRE.
FRE = cipherfn.encrypt(FR);
// 12. FRE is xored with the next 8 octets of plaintext, to produce the
// next 8 octets of ciphertext. These are loaded into FR and the
// process is repeated until the plaintext is used up.
for (i = 0; i < block_size; i++) ciphertext += String.fromCharCode(FRE[i] ^ plaintext.charCodeAt((n - 2) +
i));
}
} else {
plaintext = " " + plaintext;
// 9. FRE is xored with the first 8 octets of the given plaintext, now
// that we have finished encrypting the 10 octets of prefixed data.
// This produces C11-C18, the next 8 octets of ciphertext.
for (i = 2; i < block_size; i++) ciphertext += String.fromCharCode(FRE[i] ^ plaintext.charCodeAt(i));
var tempCiphertext = ciphertext.substring(0, 2 * block_size).split('');
var tempCiphertextString = ciphertext.substring(block_size);
for (n = block_size; n < plaintext.length; n += block_size) {
// 10. FR is loaded with C11-C18
for (i = 0; i < block_size; i++) FR[i] = tempCiphertextString.charCodeAt(i);
tempCiphertextString = '';
// 11. FR is encrypted to produce FRE.
FRE = cipherfn.encrypt(FR);
// 12. FRE is xored with the next 8 octets of plaintext, to produce the
// next 8 octets of ciphertext. These are loaded into FR and the
// process is repeated until the plaintext is used up.
for (i = 0; i < block_size; i++) {
tempCiphertext.push(String.fromCharCode(FRE[i] ^ plaintext.charCodeAt(n + i)));
tempCiphertextString += String.fromCharCode(FRE[i] ^ plaintext.charCodeAt(n + i));
}
}
ciphertext = tempCiphertext.join('');
}
ciphertext = ciphertext.substring(0, plaintext.length + 2 + block_size);
return ciphertext;
},
/**
* Decrypts the prefixed data for the Modification Detection Code (MDC) computation
* @param {String} cipherfn.encrypt Cipher function to use,
* @see module:crypto/cipher.
* @param {String} key binary string representation of key to be used to check the mdc
* This will be passed to the cipherfn
* @param {String} ciphertext The encrypted data
* @return {String} plaintext Data of D(ciphertext) with blocksize length +2
*/
mdc: function(cipherfn, key, ciphertext) {
cipherfn = new cipher[cipherfn](key);
var block_size = cipherfn.blockSize;
var iblock = new Array(block_size);
var ablock = new Array(block_size);
var i;
// initialisation vector
for (i = 0; i < block_size; i++) iblock[i] = 0;
iblock = cipherfn.encrypt(iblock);
for (i = 0; i < block_size; i++) {
ablock[i] = ciphertext.charCodeAt(i);
iblock[i] ^= ablock[i];
}
ablock = cipherfn.encrypt(ablock);
return util.bin2str(iblock) +
String.fromCharCode(ablock[0] ^ ciphertext.charCodeAt(block_size)) +
String.fromCharCode(ablock[1] ^ ciphertext.charCodeAt(block_size + 1));
},
/**
* This function decrypts a given plaintext using the specified
* blockcipher to decrypt a message
* @param {String} cipherfn the algorithm cipher class to decrypt
* data in one block_size encryption, {@link module:crypto/cipher}.
* @param {String} key binary string representation of key to be used to decrypt the ciphertext.
* This will be passed to the cipherfn
* @param {String} ciphertext to be decrypted provided as a string
* @param {Boolean} resync a boolean value specifying if a resync of the
* IV should be used or not. The encrypteddatapacket uses the
* "old" style with a resync. Decryption within an
* encryptedintegrityprotecteddata packet is not resyncing the IV.
* @return {String} a string with the plaintext data
*/
decrypt: function(cipherfn, key, ciphertext, resync) {
cipherfn = new cipher[cipherfn](key);
var block_size = cipherfn.blockSize;
var iblock = new Array(block_size);
var ablock = new Array(block_size);
var i, n = '';
var text = [];
// initialisation vector
for (i = 0; i < block_size; i++) iblock[i] = 0;
iblock = cipherfn.encrypt(iblock, key);
for (i = 0; i < block_size; i++) {
ablock[i] = ciphertext.charCodeAt(i);
iblock[i] ^= ablock[i];
}
ablock = cipherfn.encrypt(ablock, key);
// test check octets
if (iblock[block_size - 2] != (ablock[0] ^ ciphertext.charCodeAt(block_size)) || iblock[block_size - 1] != (ablock[
1] ^ ciphertext.charCodeAt(block_size + 1))) {
throw new Error('Invalid data.');
}
/* RFC4880: Tag 18 and Resync:
* [...] Unlike the Symmetrically Encrypted Data Packet, no
* special CFB resynchronization is done after encrypting this prefix
* data. See "OpenPGP CFB Mode" below for more details.
*/
if (resync) {
for (i = 0; i < block_size; i++) iblock[i] = ciphertext.charCodeAt(i + 2);
for (n = block_size + 2; n < ciphertext.length; n += block_size) {
ablock = cipherfn.encrypt(iblock);
for (i = 0; i < block_size && i + n < ciphertext.length; i++) {
iblock[i] = ciphertext.charCodeAt(n + i);
text.push(String.fromCharCode(ablock[i] ^ iblock[i]));
}
}
} else {
for (i = 0; i < block_size; i++) iblock[i] = ciphertext.charCodeAt(i);
for (n = block_size; n < ciphertext.length; n += block_size) {
ablock = cipherfn.encrypt(iblock);
for (i = 0; i < block_size && i + n < ciphertext.length; i++) {
iblock[i] = ciphertext.charCodeAt(n + i);
text.push(String.fromCharCode(ablock[i] ^ iblock[i]));
}
}
}
n = resync ? 0 : 2;
text = text.join('');
text = text.substring(n, ciphertext.length - block_size - 2 + n);
return text;
},
normalEncrypt: function(cipherfn, key, plaintext, iv) {
cipherfn = new cipher[cipherfn](key);
var block_size = cipherfn.blockSize;
var blocki = "";
var blockc = "";
var pos = 0;
var cyphertext = [];
var tempBlock = [];
blockc = iv.substring(0, block_size);
while (plaintext.length > block_size * pos) {
var encblock = cipherfn.encrypt(util.str2bin(blockc));
blocki = plaintext.substring((pos * block_size), (pos * block_size) + block_size);
for (var i = 0; i < blocki.length; i++)
tempBlock.push(String.fromCharCode(blocki.charCodeAt(i) ^ encblock[i]));
blockc = tempBlock.join('');
tempBlock = [];
cyphertext.push(blockc);
pos++;
}
return cyphertext.join('');
},
normalDecrypt: function(cipherfn, key, ciphertext, iv) {
cipherfn = new cipher[cipherfn](key);
var block_size = cipherfn.blockSize;
var blockp = "";
var pos = 0;
var plaintext = [];
var offset = 0;
var i;
if (iv === null)
for (i = 0; i < block_size; i++) blockp += String.fromCharCode(0);
else
blockp = iv.substring(0, block_size);
while (ciphertext.length > (block_size * pos)) {
var decblock = cipherfn.encrypt(util.str2bin(blockp));
blockp = ciphertext.substring((pos * (block_size)) + offset, (pos * (block_size)) + (block_size) + offset);
for (i = 0; i < blockp.length; i++) {
plaintext.push(String.fromCharCode(blockp.charCodeAt(i) ^ decblock[i]));
}
pos++;
}
return plaintext.join('');
}
};
</code></pre>
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