publicEncrypt.js
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var parseKeys = require('parse-asn1');
var randomBytes = require('randombytes');
var createHash = require('create-hash');
var mgf = require('./mgf');
var xor = require('./xor');
var bn = require('bn.js');
var withPublic = require('./withPublic');
var crt = require('browserify-rsa');
var constants = {
RSA_PKCS1_OAEP_PADDING: 4,
RSA_PKCS1_PADDIN: 1,
RSA_NO_PADDING: 3
};
module.exports = function publicEncrypt(public_key, msg, reverse) {
var padding;
if (public_key.padding) {
padding = public_key.padding;
} else if (reverse) {
padding = 1;
} else {
padding = 4;
}
var key = parseKeys(public_key);
var paddedMsg;
if (padding === 4) {
paddedMsg = oaep(key, msg);
} else if (padding === 1) {
paddedMsg = pkcs1(key, msg, reverse);
} else if (padding === 3) {
paddedMsg = new bn(msg);
if (paddedMsg.cmp(key.modulus) >= 0) {
throw new Error('data too long for modulus');
}
} else {
throw new Error('unknown padding');
}
if (reverse) {
return crt(paddedMsg, key);
} else {
return withPublic(paddedMsg, key);
}
};
function oaep(key, msg){
var k = key.modulus.byteLength();
var mLen = msg.length;
var iHash = createHash('sha1').update(new Buffer('')).digest();
var hLen = iHash.length;
var hLen2 = 2 * hLen;
if (mLen > k - hLen2 - 2) {
throw new Error('message too long');
}
var ps = new Buffer(k - mLen - hLen2 - 2);
ps.fill(0);
var dblen = k - hLen - 1;
var seed = randomBytes(hLen);
var maskedDb = xor(Buffer.concat([iHash, ps, new Buffer([1]), msg], dblen), mgf(seed, dblen));
var maskedSeed = xor(seed, mgf(maskedDb, hLen));
return new bn(Buffer.concat([new Buffer([0]), maskedSeed, maskedDb], k));
}
function pkcs1(key, msg, reverse){
var mLen = msg.length;
var k = key.modulus.byteLength();
if (mLen > k - 11) {
throw new Error('message too long');
}
var ps;
if (reverse) {
ps = new Buffer(k - mLen - 3);
ps.fill(0xff);
} else {
ps = nonZero(k - mLen - 3);
}
return new bn(Buffer.concat([new Buffer([0, reverse?1:2]), ps, new Buffer([0]), msg], k));
}
function nonZero(len, crypto) {
var out = new Buffer(len);
var i = 0;
var cache = randomBytes(len*2);
var cur = 0;
var num;
while (i < len) {
if (cur === cache.length) {
cache = randomBytes(len*2);
cur = 0;
}
num = cache[cur++];
if (num) {
out[i++] = num;
}
}
return out;
}