decrypt block
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@ -1,5 +1,6 @@
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var Random = require('../random');
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// Cipher Block Chaining
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// http://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Cipher-block_chaining_.28CBC.29
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var CBC = function CBC(blockcipher, cipherkeybuf, ivbuf) {
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if (!(this instanceof CBC))
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@ -40,6 +41,12 @@ CBC.encryptblock = function(blockbuf, ivbuf, blockcipher, cipherkeybuf) {
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return encbuf;
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};
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CBC.decryptblock = function(encbuf, ivbuf, blockcipher, cipherkeybuf) {
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var xorbuf = blockcipher.decrypt(encbuf, cipherkeybuf);
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var blockbuf = CBC.xorbufs(xorbuf, ivbuf);
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return blockbuf;
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};
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CBC.encryptblocks = function(blockbufs, ivbuf, blockcipher, cipherkeybuf) {
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var encbufs = [];
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@ -55,6 +62,21 @@ CBC.encryptblocks = function(blockbufs, ivbuf, blockcipher, cipherkeybuf) {
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return encbufs;
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};
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CBC.decryptblocks = function(encbufs, ivbuf, blockcipher, cipherkeybuf) {
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var blockbufs = [];
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for (var i = 0; i < encbufs.length; i++) {
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var encbuf = encbufs[i];
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var blockbuf = CBC.decryptblock(encbuf, ivbuf, blockcipher, cipherkeybuf);
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blockbufs.push(blockbuf);
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ivbuf = encbuf;
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}
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return encbufs;
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};
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CBC.pkcs7pad = function(buf, blocksize) {
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var bytesize = blocksize / 8;
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var padbytesize = bytesize - buf.length;
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@ -90,6 +90,29 @@ describe('CBC', function() {
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});
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describe('@decryptblock', function() {
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it('should decrypt an encrypted block', function() {
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var messagebuf = new Buffer(128 / 8);
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messagebuf.fill(0);
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var ivbuf = new Buffer(128 / 8);
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ivbuf.fill(0x10);
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var cipherkeybuf = new Buffer(128 / 8);
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cipherkeybuf.fill(0);
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var blockcipher = {};
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blockcipher.encrypt = function(messagebuf, cipherkeybuf) {
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return messagebuf;
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};
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blockcipher.decrypt = function(messagebuf, cipherkeybuf) {
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return messagebuf;
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};
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var encbuf = CBC.encryptblock(messagebuf, ivbuf, blockcipher, cipherkeybuf);
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var buf = CBC.decryptblock(encbuf, ivbuf, blockcipher, cipherkeybuf);
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buf.toString('hex').should.equal(messagebuf.toString('hex'));
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});
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});
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describe('@encryptblocks', function() {
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it('should return this known value', function() {
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