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SHA-256 Hash (sha256)

SHA-256 secure hash algorithm, 256-bit digest computation. Supports one-shot and streaming interfaces.

Constants and Data Structure​

#define SHA256_DIGEST_SIZE (32)

struct sha256_ctx_t {
    uint64_t count;
    uint8_t buf[64];
    uint32_t state[8];
};

API​

One-shot​

const uint8_t * sha256_hash(const void * data, int len, uint8_t * digest);
  • data — Input data
  • len — Data length
  • digest — Output 32-byte digest

Returns digest pointer.

Streaming​

void sha256_init(struct sha256_ctx_t * ctx);
void sha256_update(struct sha256_ctx_t * ctx, const void * data, int len);
const uint8_t * sha256_final(struct sha256_ctx_t * ctx);
  • sha256_init — Initialize context
  • sha256_update — Feed data, may be called multiple times
  • sha256_final — Finalize and return digest pointer (points to internal context buffer)

Example​

One-shot​

uint8_t msg[] = { 'x', 'b', 'o', 'o', 't' };
uint8_t digest[SHA256_DIGEST_SIZE];
sha256_hash(msg, sizeof(msg), digest);
/* digest = 0xa81a87bd a68abf88 8b64aa20 c6cf204b
           91889afa 1a8506b1 e4125acb 372edb0d */

Streaming​

struct sha256_ctx_t ctx;
uint8_t digest[SHA256_DIGEST_SIZE];

sha256_init(&ctx);
sha256_update(&ctx, chunk1, len1);
sha256_update(&ctx, chunk2, len2);
sha256_final(&ctx);