sha256clib is a library of functions written in C to calculate and manipulate SHA-256 digests. It includes the following:
| Function | Description |
|---|---|
| void sha256_printDigestAsHex(uint32_t* digest); | Prints a binary sha-256 digest to stdio in hexidecimal format. |
| void sha256_digestToHex(uint32_t* digest, char* str); | Converts a binary sha-256 digest into a null terimated string in hexidecimal format. |
| void sha256_hexToDigest(char* str, uint32_t* digest); | Converts a sha-256 digest from a null terminated hexidecimal string into binary format. |
| bool sha256_digestsAreEqual(uint32_t* digest1, uint32_t* digest2); | Compares two binary sha-256 digests for equality. |
| bool sha256_binToDigest(uint8_t* buffer, size_t byteCount, uint32_t* digest); | Calculates a sha-256 digest from data in buffer and writes it to digest. |
| bool sha256_fileToDigest(FILE* f, uint32_t* digest); | Calculates a sha-256 hash digest from a file and writes it to digest. |
Please note the following before attempting to use sha256clib :
- sha256clib was not designed or tested for muliprocessing.
- sha256clib was designed for use and tested on little-endian machines only.
- A sha-256 digest is always an array of 8 32-bit integers (for example, uint32_t digest[8];)
- The null terminated hexidecimal string representation of a sha-256 digest is always an array of 64 bytes terminated by an additional null character, for a total of 65 bytes.
The accompanying makefile is designed to build a shared library on Linux. You can modify the location of the shared library by changing the libpath variable on the second line of the makefile. It also generates an executable called calcsha256, which calculates a digest from a file path provided as a command line argument similar to sha256sum.
sha256clib is licensed under the Boost Software License - Version 1.0 - August 17th, 2003.
The following are suggested resources for anyone interested in understanding how the sha-256 algorithm works.: