HAL_GCM_ALT

MBEDTLS IMPLEMENTATION HAL GCM ALT FUNCTIONS

group MBEDTLS_IMPLEMENTATION_HAL_GCM_ALT_FUNCTIONS

Public API functions for HAL GCM alternate implementation.

Functions

void mbedtls_gcm_init ( mbedtls_gcm_context * ctx )

int mbedtls_gcm_setkey ( mbedtls_gcm_context * ctx , mbedtls_cipher_id_t cipher , const unsigned char * key , unsigned int keybits )

int mbedtls_gcm_starts ( mbedtls_gcm_context * ctx , int mode , const unsigned char * iv , size_t iv_len )

int mbedtls_gcm_update_ad ( mbedtls_gcm_context * ctx , const unsigned char * add , size_t add_len )

Details on the state variables in mbedtls_gcm_context.

mbedtls_gcm_context::buf contains the partial state of the computation of the authentication tag.

mbedtls_gcm_context::add_len and mbedtls_gcm_context::len indicate different stages of the computation:

• len == 0 && add_len == 0: Initial state.

• len == 0 && add_len % 16 != 0: The first add_len % 16 bytes have a partial block of AD that has been xored in but not yet multiplied in.

• len == 0 && add_len % 16 == 0: The authentication tag is correct if the data ends now.

• len % 16 != 0: The first len % 16 bytes have a partial block of ciphertext that has been xored in but not yet multiplied in.

• len > 0 && len % 16 == 0: The authentication tag is correct if the data ends now.

int mbedtls_gcm_update ( mbedtls_gcm_context * ctx , const unsigned char * input , size_t input_length , unsigned char * output , size_t output_size , size_t * output_length )

int mbedtls_gcm_finish ( mbedtls_gcm_context * ctx , unsigned char * output , size_t output_size , size_t * output_length , unsigned char * tag , size_t tag_len )

int mbedtls_gcm_crypt_and_tag ( mbedtls_gcm_context * ctx , int mode , size_t length , const unsigned char * iv , size_t iv_len , const unsigned char * add , size_t add_len , const unsigned char * input , unsigned char * output , size_t tag_len , unsigned char * tag )

int mbedtls_gcm_auth_decrypt ( mbedtls_gcm_context * ctx , size_t length , const unsigned char * iv , size_t iv_len , const unsigned char * add , size_t add_len , const unsigned char * tag , size_t tag_len , const unsigned char * input , unsigned char * output )

void mbedtls_gcm_free ( mbedtls_gcm_context * ctx )

MBEDTLS IMPLEMENTATION HAL GCM TYPES

group MBEDTLS_IMPLEMENTATION_HAL_GCM_TYPES

This file contains GCM definitions and functions based on STM32 AES hardware crypto accelerator.

The Galois/Counter Mode (GCM) for 128-bit block ciphers is defined in D. McGrew, J. Viega, The Galois/Counter Mode of Operation (GCM), Natl. Inst. Stand. Technol.

For more information on GCM, see NIST SP 800-38D: Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC .

GCM context structure definitions for mbedTLS HAL.

struct mbedtls_gcm_context

#include <hal_gcm_alt.h>

AES context structure.

Public Members

unsigned char y [ 16 ]

The Y working value.

unsigned char buf [ 16 ]

The buf working value.

int mode

Mode : encrypt or decrypt

uint8_t aes_key [ 32 ]

Encryption/Decryption key

size_t aes_key_size

Aes Key size

cmox_cipher_handle_t * cipher_ctx

Cipher ctx

cmox_gcm_handle_t gcm_ctx

Gcm ctx