curve25519nxt

Curve 25519 javascript implementation

The implementation is port of wonderful stuff that floodyberry did to tune up "donna" implmentation.

Original donna can be found here: https://github.com/agl/curve25519-donna

Floodyberry's implementaton can be found here: https://github.com/floodyberry/curve25519-donna

My JS port requires typed arrays support.

Sign/validate is based on "xmath's" EC-KCDSA code from sci.crypt (which is what Nxt implementation uses).

Crypto object api

Crypto object is just a wrapper for CryptoImpl object, to fulfill requirements of the bounty. All arguments and returned values have the form of hexstrings.

c = new Crypto();

• signature = c.sign(pass, message)
• isOk = c.verify(sigature, message, signersPublicKey)
• pubKey = c.getPublicKey(pass)

Keep in mind: Sign could be TWICE as fast, if signer's public key was cached! (sign first has to generate user's PK from pass, than generate Signature's PK, these operations are time consuming)

Examples

Signing.

var c = new Crypto();

// 'nxt'
var privKey = '6e7874';
var message = '5768617420676f657320726f756e642c20636f6d65732061726f756e642e';
var sigPub = c.sign(privKey, message);

Verifying

var c = new Crypto();

var pk='7c3ff12215636a7b246dea25d5e446a91fa59a9150c6ed50d8126ee86a648b68';
var msg='0000a9d63800a0057c3ff12215636a7b246dea25d5e446a91fa59a9150c6ed50d8126ee86a648b687e2fad81dbf18f2da086010064000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000';
var sig='4f0626ccd4edebb17e9d06e928b5b4e944aa7ef88a111081919794a3e265c206f9d9b0ce42a8d2e7f6d902a172159bcd39dcaab8468373258fccea9e5d2ed319'

var isOk = c.verify(sig, msg, pk);

Public Key (probably shouldn't be used, as most times, you'll have signer's key somewhere already)

var c = new Crypto();

var privKey = '6e7874';
var message = '5768617420676f657320726f756e642c20636f6d65732061726f756e642e';
var sigPub = 'b4cafe10e21676c4642354cba102243f0138b798af689ea51576a77b9013790b2b9d6470737f748e4bf449eecfee790f483dd894f17bf9a287120b6906228746';

var key = c.getPublicKey(privKey);

var isOk = c.verify(sigPub, message, key);

Results on my machine

Time for 100 signs / verify given in ms.

Keep in mind that 'sign' operation itself is very fast, what is slow are two calls to curve.

platform	Opera 19	Chrome 32	FF 26
sign	1489	1481	1634
verify	1199	1199	1098

CryptoImpl object api

c = new CryptoImpl();

• res = c.getPublicKey(pass)
  • pass - array with byte values
  • res - public key, 32b Uint8Array
• res = c.sign(pass, message)
  • pass - array with byte values
  • message - array with byte values
  • x
  • res.sig - 64b Uint8Array
  • res.key - public key, 32b Uint8Array
• res = c.verify(sig, message, publicKey)
  • sig - 64b Uint8Array as returned by .sign()
  • message - array with byte values
  • publicKey - 32b Uint8Array, from .getPublicKey() or .sign() whichever is more convenient