sha256.js

function rotateRight(value, rot) {
  return (value >>> rot) | (value << (32 - rot))
}

const K = new Uint32Array([
  0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1,
  0x923f82a4, 0xab1c5ed5, 0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
  0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174, 0xe49b69c1, 0xefbe4786,
  0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
  0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147,
  0x06ca6351, 0x14292967, 0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
  0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85, 0xa2bfe8a1, 0xa81a664b,
  0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
  0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a,
  0x5b9cca4f, 0x682e6ff3, 0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
  0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2,
])

function sha256(bytes) {
  const H = new Uint32Array([ 0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a, 0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19 ])

  const padded = new Uint8Array((bytes.length + 9 + 63) & ~63)
  padded.set(bytes)
  padded[bytes.length] = 0x80
  let dv = new DataView(padded.buffer)
  dv.setUint32(padded.length - 4, bytes.length << 3, false)

  let w = new Uint32Array(64)
  for (let i = 0; i < padded.length; i += 64) {
    for (let j = 0; j < 16; j += 1) {
      w[j] = (padded[i + 4 * j] << 24) |
          (padded[i + 4 * j + 1] << 16) |
          (padded[i + 4 * j + 2] << 8) |
          padded[i + 4 * j + 3]
    }
    for (let j = 16; j < 64; j += 1) {
      let w1 = w[j - 15]
      let w2 = w[j - 2]
      let s0 = rotateRight(w1, 7) ^ rotateRight(w1, 18) ^ (w1 >>> 3)
      let s1 = rotateRight(w2, 17) ^ rotateRight(w2, 19) ^ (w2 >>> 10)
      w[j] = w[j - 16] + s0 + w[j - 7] + s1
    }

    let [a, b, c, d, e, f, g, h] = H
    for (let j = 0; j < 64; j += 1) {
      let S1 = rotateRight(e, 6) ^ rotateRight(e, 11) ^ rotateRight(e, 25)
      let ch = (e & f) ^ (~e & g)
      let tmp1 = h + S1 + ch + K[j] + w[j]
      let S0 = rotateRight(a, 2) ^ rotateRight(a, 13) ^ rotateRight(a, 22)
      let maj = (a & b) ^ (a & c) ^ (b & c)
      let tmp2 = S0 + maj
      h = g
      g = f
      f = e
      e = d + tmp1
      d = c
      c = b
      b = a
      a = tmp1 + tmp2
    }

    H[0] += a
    H[1] += b
    H[2] += c
    H[3] += d
    H[4] += e
    H[5] += f
    H[6] += g
    H[7] += h
  }

  const hash = new Uint8Array(32)
  for (let i = 0; i < 8; i++) {
    hash[i * 4] = (H[i] >>> 24) & 0xff
    hash[i * 4 + 1] = (H[i] >>> 16) & 0xff
    hash[i * 4 + 2] = (H[i] >>> 8) & 0xff
    hash[i * 4 + 3] = H[i] & 0xff
  }
  return hash
}


/**
 * Returns a hex SHA-256 digest of an UTF-8 input string.
 *
 * @param {string} input
 * @returns {string} hex digest
 */
export function sha256Digest(input) {
  const bytes = new TextEncoder().encode(input)
  const hash = sha256(bytes)
  return Array.from(new Uint8Array(hash)).map(b => b.toString(16).padStart(2, "0")).join("")
}