README.md

scryptsy

scryptsy is a pure Javascript implementation of the scrypt key derivation function that is fully compatible with Node.js and the browser (via Browserify).

Why?

Scrypt is an integral part of many crypto currencies. It's a part of the BIP38 standard for encrypting private Bitcoin keys. It also serves as the proof-of-work system for many crypto currencies, most notably: Litecoin and Dogecoin.

Installation

npm install --save scryptsy

Browserify Note

When using a browserified bundle, be sure to add setImmediate as a shim.

Example

const scrypt = require('scryptsy')

async function main () {
  var key = "pleaseletmein"
  var salt = "SodiumChloride"
  var data1 = scrypt(key, salt, 16384, 8, 1, 64)
  console.log(data1.toString('hex'))
  // => 7023bdcb3afd7348461c06cd81fd38ebfda8fbba904f8e3ea9b543f6545da1f2d5432955613f0fcf62d49705242a9af9e61e85dc0d651e40dfcf017b45575887

  // async is actually slower, but it will free up the event loop occasionally
  // which will allow for front end GUI elements to update and cause it to not
  // freeze up.
  // See benchmarks below
  // Passing 300 below means every 300 iterations internally will call setImmediate once
  var data2 = await scrypt.async(key, salt, 16384, 8, 1, 64, undefined, 300)
  console.log(data2.toString('hex'))
  // => 7023bdcb3afd7348461c06cd81fd38ebfda8fbba904f8e3ea9b543f6545da1f2d5432955613f0fcf62d49705242a9af9e61e85dc0d651e40dfcf017b45575887
}
main().catch(console.error)

Benchmarks

Internal iterations are N * p, so changing r doesn't affect the number of calls to setImmediate. Decreasing pI decreases performance in exchange for more frequently freeing the event loop. (pI Default is 5000 loops per setImmediate call)

Note: these benchmarks were done on node v10 on a CPU with good single thread performance. browsers show a much larger difference. Please tinker with the pI setting to balance between performance and GUI responsiveness.

If pI >= N, setImmediate will only be called p * 2 times total (on the i = 0 of each for loop).

---------------------------
time    : type : (N,r,p,pI) (pI = promiseInterval)
---------------------------
2266 ms :  sync (2^16,16,1)
2548 ms : async (2^16,16,1,5000)
12.44% increase
---------------------------
2616 ms :  sync (2^16,1,16)
2995 ms : async (2^16,1,16,5000)
14.49% increase
---------------------------
2685 ms :  sync (2^20,1,1)
3090 ms : async (2^20,1,1,5000)
15.08% increase
---------------------------
2235 ms :  sync (2^16,16,1)
2627 ms : async (2^16,16,1,10)
17.54% increase
---------------------------
2592 ms :  sync (2^16,1,16)
3305 ms : async (2^16,1,16,10)
27.51% increase
---------------------------
2705 ms :  sync (2^20,1,1)
3363 ms : async (2^20,1,1,10)
24.33% increase
---------------------------
2278 ms :  sync (2^16,16,1)
2773 ms : async (2^16,16,1,1)
21.73% increase
---------------------------
2617 ms :  sync (2^16,1,16)
5632 ms : async (2^16,1,16,1)
115.21% increase
---------------------------
2727 ms :  sync (2^20,1,1)
5723 ms : async (2^20,1,1,1)
109.86% increase
---------------------------

API

scrypt(key, salt, N, r, p, keyLenBytes, [progressCallback])

• key: The key. Either Buffer or string.
• salt: The salt. Either Buffer or string.
• N: The number of iterations. number (integer)
• r: Memory factor. number (integer)
• p: Parallelization factor. number (integer)
• keyLenBytes: The number of bytes to return. number (integer)
• progressCallback: Call callback on every 1000 ops. Passes in {current, total, percent} as first parameter to progressCallback().

Returns Buffer.

scrypt.async(key, salt, N, r, p, keyLenBytes, [progressCallback, promiseInterval])

• key: The key. Either Buffer or string.
• salt: The salt. Either Buffer or string.
• N: The number of iterations. number (integer)
• r: Memory factor. number (integer)
• p: Parallelization factor. number (integer)
• keyLenBytes: The number of bytes to return. number (integer)
• progressCallback: Call callback on every 1000 ops. Passes in {current, total, percent} as first parameter to progressCallback().
• promiseInterval: The number of internal iterations before calling setImmediate once to free the event loop.

Returns Promise<Buffer>.

Resources

• Tarsnap Blurb on Scrypt
• Scrypt Whitepaper
• IETF Scrypt (Test vector params are incorrect.)

License

MIT