react-native-scryptsy

react-native-scryptsy is a pure Javascript implementation of the scrypt key derivation function that is fully compatible with React Native and expo.

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 react-native-scryptsy

Example

const scrypt = require('react-native-scryptsy')

async function main () {
  var key = "pleaseletmein"
  var salt = "SodiumChloride"
  var hash = scrypt(key, salt, 16384, 8, 1, 64)
  console.log(hash.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 hash2 = await scrypt.async(key, salt, 16384, 8, 1, 64, undefined, 300)
  console.log(hash2.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