freeCodeCamp/curriculum/challenges/english/10-coding-interview-prep/rosetta-code/sha-256.md

---
id: 5eb3e4c3a894c333d2811a3f
title: SHA-256
challengeType: 5
forumTopicId: 385328
dashedName: sha-256
---

# --description--

**[SHA-256](https://en.wikipedia.org/wiki/SHA-256)** is the recommended stronger alternative to [SHA-1](https://rosettacode.org/wiki/SHA-1).

# --instructions--

Write a function that takes a string as a parameter and returns its SHA-256 digest.

# --hints--

`SHA256` should be a function.

```js
assert(typeof SHA256 === 'function');
```

`SHA256("Rosetta code")` should return a string.

```js
assert(typeof SHA256('Rosetta code') === 'string');
```

`SHA256("Rosetta code")` should return `"764faf5c61ac315f1497f9dfa542713965b785e5cc2f707d6468d7d1124cdfcf"`.

```js
assert.equal(
  SHA256('Rosetta code'),
  '764faf5c61ac315f1497f9dfa542713965b785e5cc2f707d6468d7d1124cdfcf'
);
```

`SHA256("SHA-256 Hash")` should return `"bee8c0cabdcf8c7835f40217dd35a8b0dba9134520e633f1c57285f35ca7ee3e"`.

```js
assert.equal(
  SHA256('SHA-256 Hash'),
  'bee8c0cabdcf8c7835f40217dd35a8b0dba9134520e633f1c57285f35ca7ee3e'
);
```

`SHA256("implementation")` should return `"da31012c40330e7e21538e7dd57503b16e8a0839159e96137090cccc9910b171"`.

```js
assert.equal(
  SHA256('implementation'),
  'da31012c40330e7e21538e7dd57503b16e8a0839159e96137090cccc9910b171'
);
```

`SHA256("algorithm")` should return `"b1eb2ec8ac9f31ff7918231e67f96e6deda83a9ff33ed2c67443f1df81e5ed14"`.

```js
assert.equal(
  SHA256('algorithm'),
  'b1eb2ec8ac9f31ff7918231e67f96e6deda83a9ff33ed2c67443f1df81e5ed14'
);
```

`SHA256("language")` should return `"a4ef304ba42a200bafd78b046e0869af9183f6eee5524aead5dcb3a5ab5f8f3f"`.

```js
assert.equal(
  SHA256('language'),
  'a4ef304ba42a200bafd78b046e0869af9183f6eee5524aead5dcb3a5ab5f8f3f'
);
```

# --seed--

## --seed-contents--

```js
function SHA256(input) {

}
```

# --solutions--

```js
function SHA256(input) {
  var chrsz = 8;
  var hexcase = 0;

  function safe_add(x, y) {
    var lsw = (x & 0xffff) + (y & 0xffff);
    var msw = (x >> 16) + (y >> 16) + (lsw >> 16);
    return (msw << 16) | (lsw & 0xffff);
  }

  function S(X, n) {
    return (X >>> n) | (X << (32 - n));
  }

  function R(X, n) {
    return X >>> n;
  }

  function Ch(x, y, z) {
    return (x & y) ^ (~x & z);
  }

  function Maj(x, y, z) {
    return (x & y) ^ (x & z) ^ (y & z);
  }

  function Sigma0256(x) {
    return S(x, 2) ^ S(x, 13) ^ S(x, 22);
  }

  function Sigma1256(x) {
    return S(x, 6) ^ S(x, 11) ^ S(x, 25);
  }

  function Gamma0256(x) {
    return S(x, 7) ^ S(x, 18) ^ R(x, 3);
  }

  function Gamma1256(x) {
    return S(x, 17) ^ S(x, 19) ^ R(x, 10);
  }

  function Sigma0512(x) {
    return S(x, 28) ^ S(x, 34) ^ S(x, 39);
  }

  function Sigma1512(x) {
    return S(x, 14) ^ S(x, 18) ^ S(x, 41);
  }

  function Gamma0512(x) {
    return S(x, 1) ^ S(x, 8) ^ R(x, 7);
  }

  function Gamma1512(x) {
    return S(x, 19) ^ S(x, 61) ^ R(x, 6);
  }

  function core_sha256(m, l) {
    var K = new Array(
      0x428a2f98,
      0x71374491,
      0xb5c0fbcf,
      0xe9b5dba5,
      0x3956c25b,
      0x59f111f1,
      0x923f82a4,
      0xab1c5ed5,
      0xd807aa98,
      0x12835b01,
      0x243185be,
      0x550c7dc3,
      0x72be5d74,
      0x80deb1fe,
      0x9bdc06a7,
      0xc19bf174,
      0xe49b69c1,
      0xefbe4786,
      0xfc19dc6,
      0x240ca1cc,
      0x2de92c6f,
      0x4a7484aa,
      0x5cb0a9dc,
      0x76f988da,
      0x983e5152,
      0xa831c66d,
      0xb00327c8,
      0xbf597fc7,
      0xc6e00bf3,
      0xd5a79147,
      0x6ca6351,
      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
    );
    var HASH = new Array(
      0x6a09e667,
      0xbb67ae85,
      0x3c6ef372,
      0xa54ff53a,
      0x510e527f,
      0x9b05688c,
      0x1f83d9ab,
      0x5be0cd19
    );
    var W = new Array(64);
    var a, b, c, d, e, f, g, h, i, j;
    var T1, T2;

    m[l >> 5] |= 0x80 << (24 - (l % 32));
    m[(((l + 64) >> 9) << 4) + 15] = l;

    for (var i = 0; i < m.length; i += 16) {
      a = HASH[0];
      b = HASH[1];
      c = HASH[2];
      d = HASH[3];
      e = HASH[4];
      f = HASH[5];
      g = HASH[6];
      h = HASH[7];

      for (var j = 0; j < 64; j++) {
        if (j < 16) W[j] = m[j + i];
        else
          W[j] = safe_add(
            safe_add(
              safe_add(Gamma1256(W[j - 2]), W[j - 7]),
              Gamma0256(W[j - 15])
            ),
            W[j - 16]
          );

        T1 = safe_add(
          safe_add(safe_add(safe_add(h, Sigma1256(e)), Ch(e, f, g)), K[j]),
          W[j]
        );
        T2 = safe_add(Sigma0256(a), Maj(a, b, c));

        h = g;
        g = f;
        f = e;
        e = safe_add(d, T1);
        d = c;
        c = b;
        b = a;
        a = safe_add(T1, T2);
      }

      HASH[0] = safe_add(a, HASH[0]);
      HASH[1] = safe_add(b, HASH[1]);
      HASH[2] = safe_add(c, HASH[2]);
      HASH[3] = safe_add(d, HASH[3]);
      HASH[4] = safe_add(e, HASH[4]);
      HASH[5] = safe_add(f, HASH[5]);
      HASH[6] = safe_add(g, HASH[6]);
      HASH[7] = safe_add(h, HASH[7]);
    }
    return HASH;
  }

  function core_sha512(m, l) {
    var K = new Array(
      0x428a2f98d728ae22,
      0x7137449123ef65cd,
      0xb5c0fbcfec4d3b2f,
      0xe9b5dba58189dbbc,
      0x3956c25bf348b538,
      0x59f111f1b605d019,
      0x923f82a4af194f9b,
      0xab1c5ed5da6d8118,
      0xd807aa98a3030242,
      0x12835b0145706fbe,
      0x243185be4ee4b28c,
      0x550c7dc3d5ffb4e2,
      0x72be5d74f27b896f,
      0x80deb1fe3b1696b1,
      0x9bdc06a725c71235,
      0xc19bf174cf692694,
      0xe49b69c19ef14ad2,
      0xefbe4786384f25e3,
      0x0fc19dc68b8cd5b5,
      0x240ca1cc77ac9c65,
      0x2de92c6f592b0275,
      0x4a7484aa6ea6e483,
      0x5cb0a9dcbd41fbd4,
      0x76f988da831153b5,
      0x983e5152ee66dfab,
      0xa831c66d2db43210,
      0xb00327c898fb213f,
      0xbf597fc7beef0ee4,
      0xc6e00bf33da88fc2,
      0xd5a79147930aa725,
      0x06ca6351e003826f,
      0x142929670a0e6e70,
      0x27b70a8546d22ffc,
      0x2e1b21385c26c926,
      0x4d2c6dfc5ac42aed,
      0x53380d139d95b3df,
      0x650a73548baf63de,
      0x766a0abb3c77b2a8,
      0x81c2c92e47edaee6,
      0x92722c851482353b,
      0xa2bfe8a14cf10364,
      0xa81a664bbc423001,
      0xc24b8b70d0f89791,
      0xc76c51a30654be30,
      0xd192e819d6ef5218,
      0xd69906245565a910,
      0xf40e35855771202a,
      0x106aa07032bbd1b8,
      0x19a4c116b8d2d0c8,
      0x1e376c085141ab53,
      0x2748774cdf8eeb99,
      0x34b0bcb5e19b48a8,
      0x391c0cb3c5c95a63,
      0x4ed8aa4ae3418acb,
      0x5b9cca4f7763e373,
      0x682e6ff3d6b2b8a3,
      0x748f82ee5defb2fc,
      0x78a5636f43172f60,
      0x84c87814a1f0ab72,
      0x8cc702081a6439ec,
      0x90befffa23631e28,
      0xa4506cebde82bde9,
      0xbef9a3f7b2c67915,
      0xc67178f2e372532b,
      0xca273eceea26619c,
      0xd186b8c721c0c207,
      0xeada7dd6cde0eb1e,
      0xf57d4f7fee6ed178,
      0x06f067aa72176fba,
      0x0a637dc5a2c898a6,
      0x113f9804bef90dae,
      0x1b710b35131c471b,
      0x28db77f523047d84,
      0x32caab7b40c72493,
      0x3c9ebe0a15c9bebc,
      0x431d67c49c100d4c,
      0x4cc5d4becb3e42b6,
      0x597f299cfc657e2a,
      0x5fcb6fab3ad6faec,
      0x6c44198c4a475817
    );
    var HASH = new Array(
      0x6a09e667f3bcc908,
      0xbb67ae8584caa73b,
      0x3c6ef372fe94f82b,
      0xa54ff53a5f1d36f1,
      0x510e527fade682d1,
      0x9b05688c2b3e6c1f,
      0x1f83d9abfb41bd6b,
      0x5be0cd19137e2179
    );
    var W = new Array(80);
    var a, b, c, d, e, f, g, h, i, j;
    var T1, T2;
  }

  function str2binb(str) {
    var bin = Array();
    var mask = (1 << chrsz) - 1;
    for (var i = 0; i < str.length * chrsz; i += chrsz)
      bin[i >> 5] |= (str.charCodeAt(i / chrsz) & mask) << (24 - (i % 32));
    return bin;
  }

  function binb2str(bin) {
    var str = '';
    var mask = (1 << chrsz) - 1;
    for (var i = 0; i < bin.length * 32; i += chrsz)
      str += String.fromCharCode((bin[i >> 5] >>> (24 - (i % 32))) & mask);
    return str;
  }

  function binb2hex(binarray) {
    var hex_tab = hexcase ? '0123456789ABCDEF' : '0123456789abcdef';
    var str = '';
    for (var i = 0; i < binarray.length * 4; i++) {
      str +=
        hex_tab.charAt((binarray[i >> 2] >> ((3 - (i % 4)) * 8 + 4)) & 0xf) +
        hex_tab.charAt((binarray[i >> 2] >> ((3 - (i % 4)) * 8)) & 0xf);
    }
    return str;
  }

  function binb2b64(binarray) {
    var tab =
      'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
    var str = '';
    for (var i = 0; i < binarray.length * 4; i += 3) {
      var triplet =
        (((binarray[i >> 2] >> (8 * (3 - (i % 4)))) & 0xff) << 16) |
        (((binarray[(i + 1) >> 2] >> (8 * (3 - ((i + 1) % 4)))) & 0xff) << 8) |
        ((binarray[(i + 2) >> 2] >> (8 * (3 - ((i + 2) % 4)))) & 0xff);
      for (var j = 0; j < 4; j++) {
        if (i * 8 + j * 6 > binarray.length * 32) str += '';
        else str += tab.charAt((triplet >> (6 * (3 - j))) & 0x3f);
      }
    }
    return str;
  }

  function hex_sha2(s) {
    return binb2hex(core_sha256(str2binb(s), s.length * chrsz));
  }

  function b64_sha2(s) {
    return binb2b64(core_sha256(str2binb(s), s.length * chrsz));
  }

  function str_sha2(s) {
    return binb2str(core_sha256(str2binb(s), s.length * chrsz));
  }
  return hex_sha2(input);
}
```