This project will generate cryptographic hashes for two types of inputs. The first is a simple text string that these programs can accept via their command lines. The second input is a file, which may be of any type or extension so long as the application can open it.
The application featured here is GNU Octave. Octave is a free, open-source computing platform with a language not unlike MATLAB. There are even a few MATLAB to Octave converters available. The code below has been tested on GNU version 5.1.0.0.
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What is a Hashing Function?
As explained by the GNU website: “It is often necessary to find if two strings or files are identical. This might be done by comparing them character by character and looking for differences. However, this can be slow, and so comparing a hash of the string or file can be a rapid way of finding if the files differ.”
Hashing a String
GNU Octave version 5 introduced its “hash()” function, which replaced the now-deprecated md5sum function. This function accepts 2 strings as inputs. If it’s successful, hash() will return the hash as a hexadecimal character array.
- The first parameter must be the name of the hash (lowercase and with single or double quotes). The hash directly determines the length of the response.
- The second parameter must be the string to be hashed. This can be a string literal, for example:
>> hash('sha256','Hello world!') ans = c0535e4be2b79ffd93291305436bf889314e4a3faec05ecffcbb7df31ad9e51a…or a class (i.e. variable) of type char…
>> myString = "Hello world!"; >> hash('sha256',myString) ans = c0535e4be2b79ffd93291305436bf889314e4a3faec05ecffcbb7df31ad9e51aThe input can even be a 2-dimensional character array.
>> myArray = [ 'H' 'e' 'l' 'l' 'o' ' ' ; 'w' 'o' 'r' 'l' 'd' '!' ] myArray = Hello world! >> hash('sha256',myArray) ans = 2ec5a3f0c2fc3e6dcee0f6f3a5735a6c69d2056579a5452095b75802094043a8In total, Octave accepts the following hashes and the previously-supported MD5sum digest…
| HFUN | DESCRIPTION |
| MD2 | Message-Digest Algorithm 2 (RFC 1319) |
| MD4 | Message-Digest Algorithm 4 (RFC 1320). |
| MD5 | Message-Digest Algorithm 5 (RFC 1321) |
| SHA1 | Secure Hash Algorithm 1 (RFC 3174) |
| SHA224 | Secure Hash Algorithm 2 (224 Bits, RFC 3874) |
| SHA256 | Secure Hash Algorithm 2 (256 Bits, RFC 6234) |
| SHA384 | Secure Hash Algorithm 2 (384 Bits, RFC 6234) |
| SHA512 | Secure Hash Algorithm 2 (512 Bits, RFC 6234) |
File Content Hashing
To hash the content of a file in Octave’s working directory, replace the string with a fileread() function. Then pass fileread() the name of the file within quotation marks.
>> hash('sha256',fileread(‘myFile.txt')) ans = c0535e4be2b79ffd93291305436bf889314e4a3faec05ecffcbb7df31ad9e51aReferences
| [1] | GNU Octave Project, “Hashing Functions (GNU Octave (version 6.3.0)),” GNU Octave Project, [Online]. Available: https://docs.octave.org/v6.3.0/Hashing-Functions.html. [Accessed 17 Aug. 2022]. |
| [2] | GNU Octave Project, “Hashing Functions (GNU Octave (version 7.2.0)),” GNU Octave Project, [Online]. Available: https://docs.octave.org/v7.2.0/Hashing-Functions.html. [Accessed 17 Aug. 2022]. |
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