ssh_sha256.h File Reference

SHA-256 (FIPS 180-4) - streaming context and one-shot API. More...

#include <stddef.h>
#include <stdint.h>
#include <mbedtls/sha256.h>

Go to the source code of this file.

Classes
struct	SshSha256Ctx
	Streaming SHA-256 context. More...

Macros
#define	SSH_SHA256_DIGEST_LEN   32
	SHA-256 digest length in bytes.
#define	SSH_SHA256_BLOCK_LEN   64
	SHA-256 block size in bytes.

Functions
void	ssh_sha256_init (SshSha256Ctx *ctx)
	Initialize a streaming SHA-256 context.
void	ssh_sha256_update (SshSha256Ctx *ctx, const uint8_t *data, size_t len)
	Feed len bytes of data into the running hash.
void	ssh_sha256_final (SshSha256Ctx *ctx, uint8_t digest[SSH_SHA256_DIGEST_LEN])
	Finalize the hash and write the 32-byte digest.
void	ssh_sha256 (const uint8_t *data, size_t len, uint8_t digest[SSH_SHA256_DIGEST_LEN])
	One-shot SHA-256: hash len bytes and write the digest.

Detailed Description

SHA-256 (FIPS 180-4) - streaming context and one-shot API.

On Arduino (ESP32) targets BOTH the one-shot and the streaming context (init / update / final) delegate to mbedtls, which routes SHA-256 to the hardware accelerator. The streaming path backs the per-packet HMAC (ssh_hmac_sha256, run on every inbound and outbound SSH packet) as well as the KEX exchange-hash, so hardware acceleration matters for bulk throughput, not just the handshake. On native builds the software implementation is used.

The context therefore holds an mbedtls_sha256_context on Arduino (pulling in <mbedtls/sha256.h>) and the software hash state on native.

Author

Douglas Quigg (dstroy0)

Date

2026

Definition in file ssh_sha256.h.

Macro Definition Documentation

SSH_SHA256_DIGEST_LEN

#define SSH_SHA256_DIGEST_LEN   32

SHA-256 digest length in bytes.

Definition at line 29 of file ssh_sha256.h.

SSH_SHA256_BLOCK_LEN

#define SSH_SHA256_BLOCK_LEN   64

SHA-256 block size in bytes.

Definition at line 32 of file ssh_sha256.h.

Function Documentation

ssh_sha256_init()

void ssh_sha256_init

(

SshSha256Ctx *

ctx

)

Initialize a streaming SHA-256 context.

Parameters

ctx	Must not be NULL.

Definition at line 28 of file ssh_sha256.cpp.

References SshSha256Ctx::mbed.

Referenced by ssh_hmac_sha256_final(), ssh_hmac_sha256_init(), and ssh_kdf_derive().

ssh_sha256_update()

void ssh_sha256_update	(	SshSha256Ctx *	ctx,
		const uint8_t *	data,
		size_t	len
	)

Feed len bytes of data into the running hash.

Parameters

ctx	Initialized context.
data	Input bytes.
len	Number of input bytes.

Definition at line 38 of file ssh_sha256.cpp.

References SshSha256Ctx::mbed.

Referenced by ssh_hmac_sha256_final(), ssh_hmac_sha256_init(), ssh_hmac_sha256_update(), and ssh_kdf_derive().

ssh_sha256_final()

void ssh_sha256_final	(	SshSha256Ctx *	ctx,
		uint8_t	digest[SSH_SHA256_DIGEST_LEN]
	)

Finalize the hash and write the 32-byte digest.

The context is in an undefined state after this call; do not call update() again without first calling init().

Parameters

ctx	Initialized context with all data already fed.
digest	Output buffer, must be SSH_SHA256_DIGEST_LEN bytes.

Definition at line 47 of file ssh_sha256.cpp.

References SshSha256Ctx::mbed.

Referenced by ssh_hmac_sha256_final(), and ssh_kdf_derive().

ssh_sha256()

void ssh_sha256	(	const uint8_t *	data,
		size_t	len,
		uint8_t	digest[SSH_SHA256_DIGEST_LEN]
	)

One-shot SHA-256: hash len bytes and write the digest.

On Arduino uses the mbedtls hardware-accelerated path. On native uses the software streaming implementation.

Parameters

data	Input bytes.
len	Number of input bytes.
digest	Output buffer, must be SSH_SHA256_DIGEST_LEN bytes.

Definition at line 57 of file ssh_sha256.cpp.

Referenced by ssh_ecdsa_p256_sign(), ssh_ecdsa_p256_verify(), ssh_rsa_sign(), and ssh_rsa_verify().