GAS(Google Apps Script) user function to get MD5 hash or 4digit shortened hash for Multibyte(UTF-8, 2bytes character) environment.

md5.gs

/**
 * ------------------------------------------
 *   MD5 function for GAS(GoogleAppsScript)
 *
 * You can get a MD5 hash value and even a 4digit short Hash value of a string.
 * ------------------------------------------
 * Usage1:
 *   `=MD5("YourStringToHash")`
 *     or
 *   `=MD5( A1 )` with the same string at A1 cell
 *   result:
 *     `FCE7453B7462D9DE0C56AFCCFB756193`.
 *     For your sure-ness you can verify it in your terminal as below.
 *     `$ md5 -s "YourStringToHash"`
 * Usage2:
 *   `=MD5("YourStringToHash", true)` for short Hash
 *    result:
 *     `6MQH`
 *     Note that it has more conflict probability.
 *
 * How to install:
 *   Copy the scipt, pase it at [Tools]-[Script Editor]-[<YourProject>]
 *   or go https://script.google.com and paste it.
 *   For more details go:
 *     https://developers.google.com/apps-script/articles/
 * Latest version:
 *   https://gist.github.com/dotysan/36b99217fdc958465b62f84f66903f07
 * Author/Collaborator/Contributor:
 *   KEINOS @ https://github.com/keinos
 *   Alex Ivanov @ https://github.com/contributorpw
 +   Curtis Doty @ https://github.com/dotysan
 * Reference and thanks to:
 *   https://stackoverflow.com/questions/7994410/hash-of-a-cell-text-in-google-spreadsheet
 *   https://gist.github.com/KEINOS/78cc23f37e55e848905fc4224483763d#gistcomment-3129967
 *   https://gist.github.com/dotysan/36b99217fdc958465b62f84f66903f07
 *   https://developers.google.com/apps-script/reference/utilities/utilities#computedigestalgorithm-value
 *   https://cloud.google.com/dataprep/docs/html/Logical-Operators_57344671
 * ------------------------------------------
 *
 * @param {(string|Bytes[])} input The value to hash.
 * @param {boolean} isShortMode Set true for 4 digit shortend hash, else returns usual MD5 hash.
 * @return {string} The hashed input
 * @customfunction
 *
 */
function MD5( input, isShortMode )
{
    var isShortMode = !!isShortMode; // Be sure to be bool
    var txtHash = '';
    var rawHash = Utilities.computeDigest(
                      Utilities.DigestAlgorithm.MD5,
                      input );
 
    if ( ! isShortMode ) {
        for ( i = 0; i < rawHash.length; i++ ) {

            var hashVal = rawHash[i];

            if ( hashVal < 0 ) {
                hashVal += 256;
            };
            if ( hashVal.toString( 16 ).length == 1 ) {
                txtHash += '0';
            };
            txtHash += hashVal.toString( 16 );
        };
    } else {
        for ( j = 0; j < 16; j += 8 ) {

            hashVal = ( rawHash[j]   + rawHash[j+1] + rawHash[j+2] + rawHash[j+3] )
                    ^ ( rawHash[j+4] + rawHash[j+5] + rawHash[j+6] + rawHash[j+7] );

            if ( hashVal < 0 ) {
                hashVal += 1024;
            };
            if ( hashVal.toString( 36 ).length == 1 ) {
                txtHash += "0";
            };

            txtHash += hashVal.toString( 36 );
        };
    };

    // change below to "txtHash.toUpperCase()" if needed
    return txtHash;

}

This is brilliant! Thanks a ton :)

Does var isShortMode = !!isShortMode; work different?

@schoraria911

Thanks! Glad that it helped you!

@contributorpw

work different?

You're right. I guess it works the same. 😳 I think I just wanted to be sure at that time ...

As for me it's a cool function!

@contributorpw

thanks! ☺️

It fails to calculate md5sum for binary data. Since Utilities.computeDigest() already can handle both String and Bytes[] input, don't hard-code String!

See: https://gist.github.com/dotysan/36b99217fdc958465b62f84f66903f07

@dotysan

Utilities.computeDigest() already can handle both String and Bytes[] input

Indeed.

It seems that I was too afraid of the other encodings in Japan, such as JIS, SJIS, SJIS-WIN, EUC, ASCII.
But I realized that GAS works with UTF-8. Converting the input string encoding to UTF-8 should be the user side matter. Thanks!

I updated the script a little after all these years.

Can you give me the algorithm to decrypt it back?

@rohanchutke

Can you give me the algorithm to decrypt it back?

I would like to, but unfortunately, I can't ... sorry.

If I could, I might be nominated somehow in the encryption world or be in the breaking world news!!

Note that "hash" is not encryption nor compression. So there's no decryption or decompression as well. You may have a value that collides by calcutlation though.

One of the characteristics of the hash function is that it can not be back-calculated the original value. And another characteristic is that if you provide the same value you get the same result.

This wiki page might help you some.

• https://en.wikipedia.org/wiki/Hash_function @ Wikipedia

@KEINOS, in my outdated fork @Hash7ag asks about license. https://gist.github.com/dotysan/36b99217fdc958465b62f84f66903f07#gistcomment-3384672

@Hash7ag asks about license

@dotysan @contributorpw

MIT? Maybe? Is that OK for you two?
Personally, I don't care if it's WTFPL but I would like to respect the contribution.

Does Utilities.computeDigest require another argument Utilities.Charset.UTF_8, in order to properly handle multibyte(UTF-8, 2bytes character) environment?
I couldn't get Japanese multibyte letters processed properly with your function.