Create SHA-256 hash from a Blob/File in javascript

Question

I need to create a SHA-256 digest from a file (~6MB) inside the browser. The only way that I've managed to do it so far was like this:

var reader = new FileReader();
reader.onload = function() {
    // this gets rid of the mime-type data header
    var actual_contents = reader.result.slice(reader.result.indexOf(',') + 1);
    var what_i_need = new jsSHA(actual_contents, "B64").getHash("SHA-256", "HEX");
}
reader.readAsDataURL(some_file);

While this works correctly, the problem is that it's very slow. It took ~2-3 seconds for a 6MB file. How can I improve this?

I'm not overly familiar with the SHA256 algorithm, but if you convert the file to an ArrayBuffer then to a Uint8Array this may be faster than going via Base64 and you can work directly with the bytes. — Paul S.
– Paul S., Commented Feb 13, 2014 at 17:54
var fr = new FileReader; fr.onload = function () {var hash = byteArrayToSHA256(new Uint8Array(this.result));} fr.readAsArrayBuffer(some_file); where byteArrayToSHA256 is the hashing algorithm. This means you don't need to worry about utf-encodings/encoding-decoding base64/strings, etc. You might need to re-write the algorithm you have for this input. — Paul S.
– Paul S., Commented Feb 13, 2014 at 18:02
i would run atob() on the base64 data so that the scha script doesn't have to decode, for which it might be using a user-land base64 decoder that could be hundreds of times slower than atob()... — dandavis
– dandavis, Commented Feb 19, 2014 at 0:53
Could someone benchmark all the answers and post the results as to which would be fastest? — David542
– David542, Commented Feb 23, 2014 at 19:37

josliber · Accepted Answer · 2014-03-05 05:25:36Z

19

+500

You may want to take a look at the Stanford JS Crypto Library

GitHub

Website with Examples

From the website:

SJCL is secure. It uses the industry-standard AES algorithm at 128, 192 or 256 bits; the SHA256 hash function; the HMAC authentication code; the PBKDF2 password strengthener; and the CCM and OCB authenticated-encryption modes.

SJCL has a test page that shows how long it will take.

184 milliseconds for a SHA256 iterative. And 50 milliseconds for a SHA-256 from catameringue.

Test page

Sample code:

Encrypt data: sjcl.encrypt("password", "data")

Decrypt data: sjcl.decrypt("password", "encrypted-data")

edited Mar 5, 2014 at 5:25

josliber

44.4k12 gold badges103 silver badges136 bronze badges

answered Feb 15, 2014 at 23:34

washcloth

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1 Comment

Gabi Purcaru Over a year ago

a quick test showed that sjcl is ~10x faster than CryptoJS (for computing a SHA-256 hash for the string "1234567890"). Though it doesn't seem to support File / Blob / ArrayBuffer hashing, which brings me back to square one. From what I've found, CryptoJS is the only one that supports hashing an ArrayBuffer directly, which is way faster than going through base-64, and combined with Web Workers, it's actually usable. But if there's a way to use sjcl instead that would be way better.

Colin · Accepted Answer · 2016-06-21 18:07:20Z

8

This is an old question but I thought it's worth noting that asmCrypto is significantly faster than jsSHA, and faster than CryptoJS and SJCL

https://github.com/vibornoff/asmcrypto.js/

There is also a lite version (a fork of the above) maintained by OpenPGP.js

https://github.com/openpgpjs/asmcrypto-lite

Which only includes SHA256, and a couple of AES features.

To use asmCrypto You can simply do the following:

var sha256HexValue = asmCrypto.SHA256.hex(myArraybuffer);

I'm able to hash a 150MB+ file in < 2 seconds consistently in Chrome.

answered Jun 21, 2016 at 18:07

Colin

2,03113 silver badges28 bronze badges

1 Comment

Marco Concas Over a year ago

Do not use old versions of AsmCrypto (the code here refers to the first versions). In 2021 there is no valid documentation to use the latest version of AsmCrypto. I suggest relying on other libraries.

bilelz · Accepted Answer · 2022-11-25 13:26:05Z

7

As some have answered, it can be done in vanillajs :

async function getChecksumSha256(blob: Blob): Promise<string> {
  const uint8Array = new Uint8Array(await blob.arrayBuffer());
  const hashBuffer = await crypto.subtle.digest('SHA-256', uint8Array);
  const hashArray = Array.from(new Uint8Array(hashBuffer));

  return hashArray.map((h) => h.toString(16).padStart(2, '0')).join('');
}

Source : https://gist.github.com/bilelz/c96fb0b1f62983d061910e8d310a5162

answered Nov 25, 2022 at 13:26

bilelz

3175 silver badges3 bronze badges

1 Comment

bugmenot123 Over a year ago

Can this handle a 20GB file on a system with 1GB free RAM?

Carson · Accepted Answer · 2021-07-27 12:50:47Z

I use SubtleCrypto.digest()

test file about ~85MB, It doesn't take a second to finish.

<input type="file" multiple/>
<input placeholder="Press `Enter` when done."/>
<script>

  /**
   * @param {"SHA-1"|"SHA-256"|"SHA-384"|"SHA-512"} algorithm https://developer.mozilla.org/en-US/docs/Web/API/SubtleCrypto/digest
   * @param {string|Blob} data
   */
  async function getHash(algorithm, data) {

    const main = async (msgUint8) => { // https://developer.mozilla.org/en-US/docs/Web/API/SubtleCrypto/digest#converting_a_digest_to_a_hex_string
      const hashBuffer = await crypto.subtle.digest(algorithm, msgUint8)
      const hashArray = Array.from(new Uint8Array(hashBuffer))
      return hashArray.map(b => b.toString(16).padStart(2, '0')).join(''); // convert bytes to hex string
    }

    if (data instanceof Blob) {
      const arrayBuffer = await data.arrayBuffer()
      const msgUint8 = new Uint8Array(arrayBuffer)
      return await main(msgUint8)
    }
    const encoder = new TextEncoder()
    const msgUint8 = encoder.encode(data)
    return await main(msgUint8)
  }

  const inputFile = document.querySelector(`input[type="file"]`)
  const inputText = document.querySelector(`input[placeholder^="Press"]`)
  inputFile.onchange = async (event) => {
    for (const file of event.target.files) {
      console.log(file.name, file.type, file.size + "bytes")
      const hashHex = await getHash("SHA-256", new Blob([file]))
      console.log(hashHex)
    }
  }

  inputText.onkeyup = async (keyboardEvent) => {
    if (keyboardEvent.key === "Enter") {
      const hashHex = await getHash("SHA-256", keyboardEvent.target.value)
      console.log(hashHex)
    }
  }
</script>

Ralph Ritoch · Accepted Answer · 2014-02-22 15:02:34Z

Here is what your looking for. I derived this from a C version of the SHA256 algorithm. It also includes SHA256D. I don't think your going to get much faster than this with javascript. I tried expanding the loops and it ran slower due to optimizations run by the javascript interpreter.

// From: https://github.com/Hartland/GPL-CPU-Miner/blob/master/sha2.c

if ("undefined" == typeof vnet) {
    vnet = new Array();
}

if ("undefined" == typeof vnet.crypt) {
    vnet.crypt = new Array();
}

vnet.crypt.sha2 = function() {

    var sha256_h = [
        0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a,
        0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19
    ];

    var sha256_k = [
                    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
    ];

    var sha256_init = function(s) {
        s.state = [
                   sha256_h[0],
                   sha256_h[1],
                   sha256_h[2],
                   sha256_h[3],
                   sha256_h[4],
                   sha256_h[5],
                   sha256_h[6],
                   sha256_h[7],
        ];
    }; this.sha256_init = sha256_init;

/*
* SHA256 block compression function. The 256-bit state is transformed via
* the 512-bit input block to produce a new state.
*/
    var sha256_transform = function(s, b, swap) {

        var block = b.block;
        var state = s.state;

        var W;
        var S;
        var t0;
        var t1;
        var i;

        /* 1. Prepare message schedule W. */
        if (swap) {


            W = [
                 ((((block[0] ) << 24) & 0xff000000) | (((block[0] ) << 8) & 0x00ff0000) | (((block[0] ) >> 8) & 0x0000ff00) | (((block[0] ) >> 24) & 0x000000ff)),
                 ((((block[1] ) << 24) & 0xff000000) | (((block[1] ) << 8) & 0x00ff0000) | (((block[1] ) >> 8) & 0x0000ff00) | (((block[1] ) >> 24) & 0x000000ff)),
                 ((((block[2] ) << 24) & 0xff000000) | (((block[2] ) << 8) & 0x00ff0000) | (((block[2] ) >> 8) & 0x0000ff00) | (((block[2] ) >> 24) & 0x000000ff)),
                 ((((block[3] ) << 24) & 0xff000000) | (((block[3] ) << 8) & 0x00ff0000) | (((block[3] ) >> 8) & 0x0000ff00) | (((block[3] ) >> 24) & 0x000000ff)),
                 ((((block[4] ) << 24) & 0xff000000) | (((block[4] ) << 8) & 0x00ff0000) | (((block[4] ) >> 8) & 0x0000ff00) | (((block[4] ) >> 24) & 0x000000ff)),
                 ((((block[5] ) << 24) & 0xff000000) | (((block[5] ) << 8) & 0x00ff0000) | (((block[5] ) >> 8) & 0x0000ff00) | (((block[5] ) >> 24) & 0x000000ff)),
                 ((((block[6] ) << 24) & 0xff000000) | (((block[6] ) << 8) & 0x00ff0000) | (((block[6] ) >> 8) & 0x0000ff00) | (((block[6] ) >> 24) & 0x000000ff)),
                 ((((block[7] ) << 24) & 0xff000000) | (((block[7] ) << 8) & 0x00ff0000) | (((block[7] ) >> 8) & 0x0000ff00) | (((block[7] ) >> 24) & 0x000000ff)),
                 ((((block[8] ) << 24) & 0xff000000) | (((block[8] ) << 8) & 0x00ff0000) | (((block[8] ) >> 8) & 0x0000ff00) | (((block[8] ) >> 24) & 0x000000ff)),
                 ((((block[9] ) << 24) & 0xff000000) | (((block[9] ) << 8) & 0x00ff0000) | (((block[9] ) >> 8) & 0x0000ff00) | (((block[9] ) >> 24) & 0x000000ff)),
                 ((((block[10]) << 24) & 0xff000000) | (((block[10]) << 8) & 0x00ff0000) | (((block[10]) >> 8) & 0x0000ff00) | (((block[10]) >> 24) & 0x000000ff)),
                 ((((block[11]) << 24) & 0xff000000) | (((block[11]) << 8) & 0x00ff0000) | (((block[11]) >> 8) & 0x0000ff00) | (((block[11]) >> 24) & 0x000000ff)),
                 ((((block[12]) << 24) & 0xff000000) | (((block[12]) << 8) & 0x00ff0000) | (((block[12]) >> 8) & 0x0000ff00) | (((block[12]) >> 24) & 0x000000ff)),
                 ((((block[13]) << 24) & 0xff000000) | (((block[13]) << 8) & 0x00ff0000) | (((block[13]) >> 8) & 0x0000ff00) | (((block[13]) >> 24) & 0x000000ff)),
                 ((((block[14]) << 24) & 0xff000000) | (((block[14]) << 8) & 0x00ff0000) | (((block[14]) >> 8) & 0x0000ff00) | (((block[14]) >> 24) & 0x000000ff)),
                 ((((block[15]) << 24) & 0xff000000) | (((block[15]) << 8) & 0x00ff0000) | (((block[15]) >> 8) & 0x0000ff00) | (((block[15]) >> 24) & 0x000000ff))
            ];
        } else {
            W = [
                 block[0],
                 block[1],
                 block[2],
                 block[3],
                 block[4],
                 block[5],
                 block[6],
                 block[7],
                 block[8],
                 block[9],
                 block[10],
                 block[11],
                 block[12],
                 block[13],
                 block[14],
                 block[15]
            ];
        }


        for (i = 16; i < 64; i += 2) {
            W[i] = ((
                ((((W[i-2] >>> 17) | (W[i-2] << 15)) ^ ((W[i-2] >>> 19) | ((W[i-2] << 13)>>>0) ) ^ (W[i - 2] >>> 10)) >>> 0) + //s1 (W[i - 2]) + 
                W[i - 7] + 
                ((((W[i - 15] >>> 7) | (W[i - 15] << 25)) ^ ((W[i - 15] >>> 18) | ((W[i - 15] << 14) >>> 0)) ^ (W[i - 15] >>> 3))  >>> 0) + //s0 (W[i - 15]) + 
                W[i - 16]
            ) & 0xffffffff) >>> 0;

            W[i+1] = ((
                ((((W[i-1] >>> 17) | (W[i-1] << 15)) ^ ((W[i-1] >>> 19) | (W[i-1] << 13)) ^ (W[i - 1] >>> 10)) >>> 0)+ //s1 (W[i - 1]) + 
                W[i - 6] + 
                ((((W[i - 14] >>> 7) | (W[i - 14] << 25)) ^ ((W[i - 14] >>> 18) | (W[i - 14] << 14)) ^ (W[i - 14] >>> 3)) >>> 0)  + //s0 (W[i - 14]) + 
                W[i - 15]
            ) & 0xffffffff) >>> 0;
        }


        /* 2. Initialize working variables. */

        S = [
         state[0],
         state[1],
         state[2],
         state[3],
         state[4],
         state[5],
         state[6],
         state[7],
        ];

        /* 3. Mix. */


        i=0;
        for(;i<64;++i) {

            //RNDr(S,W,i)
            t0 = S[(71 - i) % 8] + 
                ((((S[(68 - i) % 8] >>> 6) | (S[(68 - i) % 8]  << 26)) ^ ((S[(68 - i) % 8] >>> 11) | (S[(68 - i) % 8] << 21)) ^ ((S[(68 - i) % 8] >>> 25) | (S[(68 - i) % 8] << 7)))) + //S1 (S[(68 - i) % 8]) +
                (((S[(68 - i) % 8] & (S[(69 - i) % 8] ^ S[(70 - i) % 8])) ^ S[(70 - i) % 8]) ) + // Ch
                W[i] + 
                sha256_k[i];

            t1 = ((((S[(64 - i) % 8] >>> 2) | ((S[(64 - i) % 8] & 3) << 30)) ^ ((S[(64 - i) % 8] >>> 13) | (S[(64 - i) % 8] << 19)) ^ ((S[(64 - i) % 8] >>> 22) | (S[(64 - i) % 8] << 10)))) + //S0 (S[(64 - i) % 8]) +
                (((S[(64 - i) % 8] & (S[(65 - i) % 8] | S[(66 - i) % 8])) | (S[(65 - i) % 8] & S[(66 - i) % 8]))); // Maj

            S[(67 - i) % 8] = ((S[(67 - i) % 8] + t0) & 0xFFFFFFFF) >>> 0; 
            S[(71 - i) % 8] = ((t0 + t1) & 0xFFFFFFFF) >>> 0;
        }

        /* 4. Mix local working variables into global state */

        i=0;
        for(;i<8;++i) {
            s.state[i] = (0xFFFFFFFF & (state[i] + S[i])) >>> 0;
        }

    }; this.sha256_transform = sha256_transform;

    var sha256d_hash1 = [
        0x00000000, 0x00000000, 0x00000000, 0x00000000,
        0x00000000, 0x00000000, 0x00000000, 0x00000000,
        0x80000000, 0x00000000, 0x00000000, 0x00000000,
        0x00000000, 0x00000000, 0x00000000, 0x00000100
    ];

    var sha256d_80_swap = function(hash, data) 
    {

        var S = new Array();

        var i;

        var b1 = new Array();
        var b2 = new Array();
        var b3 = new Array();

        b1.block = [
            data[0],
            data[1],
            data[2],
            data[3],
            data[4],
            data[5],
            data[6],
            data[7],
            data[8],
            data[9],
            data[10],
            data[11],
            data[12],
            data[13],
            data[14],
            data[15]
        ];

        b2.block = [
            data[16],
            data[17],
            data[18],
            data[19],
            data[20],
            data[21],
            data[22],
            data[23],
            data[24],
            data[25],
            data[26],
            data[27],
            data[28],
            data[29],
            data[30],
            data[31]
        ];

        sha256_init(S);
        sha256_transform(S, b1, 0);
        sha256_transform(S, b2, 0);

        b3.block = [
            S.state[0],
            S.state[1],
            S.state[2],
            S.state[3],
            S.state[4],
            S.state[5],
            S.state[6],
            S.state[7],
            sha256d_hash1[8],
            sha256d_hash1[9],
            sha256d_hash1[10],
            sha256d_hash1[11],
            sha256d_hash1[12],
            sha256d_hash1[13],
            sha256d_hash1[14],
            sha256d_hash1[15]
        ];

        sha256_init(hash);
        sha256_transform(hash, b3, 0);

        for (i = 0; i < 8; i++) {
            hash.state[i] = ((((hash.state[i] ) << 24) & 0xff000000) | (((hash.state[i] ) << 8) & 0x00ff0000) | (((hash.state[i] ) >> 8) & 0x0000ff00) | (((hash.state[i] ) >> 24) & 0x000000ff)); //swab32(hash[i]);
        }

    }; this.sha256d_80_swap = sha256d_80_swap;

    var sha256d = function(hash, data) {
        var S;
        var T;
        var block_in;

        S = new Array();
        T = new Array();

        T.block = [];

        var i, r;

        //hash.hash = new Array(32).join('0').split('').map(parseFloat);

        sha256_init(S);

        for (r = data.length; r > -9; r -= 64) {
            if (r < 64) {
                if (r > 0) {
                    block_in = data.slice(data.length - r,data.length);
                    block_in.push.apply(block_in, new Array(64-r).join('0').split('').map(parseFloat));
                } else {
                    block_in = new Array(64).join('0').split('').map(parseFloat);
                }
            } else {
                block_in = data.slice(data.length - r,data.length - r + 64);
            }

            //memcpy(T, data + len - r, r > 64 ? 64 : (r < 0 ? 0 : r));

            if (r >= 0 && r < 64) {
                block_in[r] = 0x80;
            } 

            for (i = 0; i < 16; i++) {
                T.block[i] = (((0xff & block_in[(i*4)]) << 24) | ((0xff & block_in[(i*4)+1]) << 16) | ((0xff & block_in[(i*4)+2]) << 8) | (0xff & block_in[(i*4)+3])) >>> 0;
            }

            if (r < 56) {
                T.block[15] = 8 * data.length;
            }

            sha256_transform(S, T, 0);
        }
        //memcpy(S + 8, sha256d_hash1 + 8, 32);
        S.block = S.state;
        for(i=8;i<16;i++) {
            S.block[i] =  sha256d_hash1[i];
        }

        sha256_init(T);
        sha256_transform(T, S, 0);

        hash.hash = [ 
                  (T.state[0] >> 24) & 0xff,
                  (T.state[0] >> 16) & 0xff,
                  (T.state[0] >> 8) & 0xff,
                  T.state[0] & 0xff,

                  (T.state[1] >> 24) & 0xff,
                  (T.state[1] >> 16) & 0xff,
                  (T.state[1] >> 8) & 0xff,
                  T.state[1] & 0xff,

                  (T.state[2] >> 24) & 0xff,
                  (T.state[2] >> 16) & 0xff,
                  (T.state[2] >> 8) & 0xff,
                  T.state[2] & 0xff,

                  (T.state[3] >> 24) & 0xff,
                  (T.state[3] >> 16) & 0xff,
                  (T.state[3] >> 8) & 0xff,
                  T.state[3] & 0xff,

                  (T.state[4] >> 24) & 0xff,
                  (T.state[4] >> 16) & 0xff,
                  (T.state[4] >> 8) & 0xff,
                  T.state[4] & 0xff,

                  (T.state[5] >> 24) & 0xff,
                  (T.state[5] >> 16) & 0xff,
                  (T.state[5] >> 8) & 0xff,
                  T.state[5] & 0xff,

                  (T.state[6] >> 24) & 0xff,
                  (T.state[6] >> 16) & 0xff,
                  (T.state[6] >> 8) & 0xff,
                  T.state[6] & 0xff,

                  (T.state[7] >> 24) & 0xff,
                  (T.state[7] >> 16) & 0xff,
                  (T.state[7] >> 8) & 0xff,
                  T.state[7] & 0xff
         ];

    }; this.sha256d = sha256d;



    var sha256 = function(hash, data) {
        var S;
        var T;
        var block_in;

        S = new Array();
        T = new Array();

        T.block = [];

        var i, r;

        hash.hash = new Array(32).join('0').split('').map(parseFloat);

        sha256_init(S);

        for (r = data.length; r > -9; r -= 64) {

            if (r < 64) {
                if (r > 0) {
                    block_in = data.slice(data.length - r,data.length);
                    block_in.push.apply(block_in, new Array(64-r).join('0').split('').map(parseFloat));
                } else {
                    block_in = new Array(64).join('0').split('').map(parseFloat);
                }
            } else {
                block_in = data.slice(data.length - r,data.length - r + 64);
            }

            //memcpy(T, data + len - r, r > 64 ? 64 : (r < 0 ? 0 : r));

            if (r >= 0 && r < 64) {
                block_in[r] = 0x80;
            } 

            for (i = 0; i < 16; i++) {
                T.block[i] = (((0xff & block_in[(i*4)]) << 24) | ((0xff & block_in[(i*4)+1]) << 16) | ((0xff & block_in[(i*4)+2]) << 8) | (0xff & block_in[(i*4)+3])) >>> 0;
            }

            if (r < 56) {
                T.block[15] = 8 * data.length;
            }

            sha256_transform(S, T, 0);
        }

        for (i = 0; i < 8; i++) {
            //be32enc((uint32_t *)hash + i, T[i]);
            hash.hash[(i * 4)] = (S.state[i] >> 24) & 0xff;
            hash.hash[(i * 4)+1] = (S.state[i] >> 16) & 0xff
            hash.hash[(i * 4)+2] = (S.state[i] >> 8) & 0xff
            hash.hash[(i * 4)+3] = S.state[i] & 0xff;
        }
    }; this.sha256 = sha256;



};

sbridges · Accepted Answer · 2014-02-16 05:09:33Z

4

It might be faster to use an emscripten compiled version of the crypto libraries,

Q. How fast will the compiled code be?

A. Emscripten's default code generation mode is in asm.js format, which is a subset of JavaScript designed to make it possible for JavaScript engines to execute very quickly. See here for up-to-date benchmark results. In many cases, asm.js can get quite close to native speed.

You can find an Emscripten-compiled NaCl cryptographic library here.

answered Feb 16, 2014 at 5:09

sbridges

25.2k4 gold badges66 silver badges72 bronze badges

Comments

Marco Concas · Accepted Answer · 2021-09-04 13:44:03Z

1

You can do that without external libraries using Crypto.subtle API. More details here.

Example:

function b2h(buffer) {
    return Array.prototype.map.call(new Uint8Array(buffer), x => ('00' + x.toString(16)).slice(-2)).join('');
}

const FILEREADER = new FileReader();
FILEREADER.readAsArrayBuffer(file);
FILEREADER.onloadend = async function(entry) {
    const FILE_HASH = b2h(await crypto.subtle.digest('SHA-256', entry.target.result)); // output: the sha256 digest hex encoded of the file
}

answered Sep 4, 2021 at 13:44

Marco Concas

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