Accelerated GCM AES-128 Cipher
Detailed Description
Accelerated AES-GCM-128 cipher for the mbed TLS API using the CRYPTOACC or SE peripheral.
This module implements the GCM AES-128 cipher, as 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.
Data Structures | |
struct | mbedtls_gcm_context |
The GCM context structure. | |
Macros | |
#define | MBEDTLS_GCM_ENCRYPT 1 |
#define | MBEDTLS_GCM_DECRYPT 0 |
#define | MBEDTLS_ERR_GCM_AUTH_FAILED -0x0012 |
#define | MBEDTLS_ERR_GCM_HW_ACCEL_FAILED -0x0013 |
#define | MBEDTLS_ERR_GCM_BAD_INPUT -0x0014 |
Functions | |
void | mbedtls_gcm_init (mbedtls_gcm_context *ctx) |
This function initializes the specified GCM context, to make references valid, and prepares the context for mbedtls_gcm_setkey() or mbedtls_gcm_free(). | |
int | mbedtls_gcm_setkey (mbedtls_gcm_context *ctx, mbedtls_cipher_id_t cipher, const unsigned char *key, unsigned int keybits) |
This function associates a GCM context with a cipher algorithm and a key. | |
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) |
This function performs GCM encryption or decryption of a buffer. | |
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) |
This function performs a GCM authenticated decryption of a buffer. | |
int | mbedtls_gcm_starts (mbedtls_gcm_context *ctx, int mode, const unsigned char *iv, size_t iv_len, const unsigned char *add, size_t add_len) |
This function starts a GCM encryption or decryption operation. | |
int | mbedtls_gcm_update (mbedtls_gcm_context *ctx, size_t length, const unsigned char *input, unsigned char *output) |
This function feeds an input buffer into an ongoing GCM encryption or decryption operation. | |
int | mbedtls_gcm_finish (mbedtls_gcm_context *ctx, unsigned char *tag, size_t tag_len) |
This function finishes the GCM operation and generates the authentication tag. | |
void | mbedtls_gcm_free (mbedtls_gcm_context *ctx) |
This function clears a GCM context and the underlying cipher sub-context. | |
Macro Definition Documentation
#define MBEDTLS_ERR_GCM_AUTH_FAILED -0x0012 |
Authenticated decryption failed.
Definition at line 71
of file gcm_alt.h
.
#define MBEDTLS_ERR_GCM_BAD_INPUT -0x0014 |
Bad input parameters to function.
Definition at line 73
of file gcm_alt.h
.
#define MBEDTLS_ERR_GCM_HW_ACCEL_FAILED -0x0013 |
GCM hardware accelerator failed.
Definition at line 72
of file gcm_alt.h
.
#define MBEDTLS_GCM_DECRYPT 0 |
Definition at line 69
of file gcm_alt.h
.
#define MBEDTLS_GCM_ENCRYPT 1 |
Definition at line 68
of file gcm_alt.h
.
Function Documentation
int mbedtls_gcm_auth_decrypt | ( | mbedtls_gcm_context * | ctx, |
size_t | length, |
||
const unsigned char * | iv, |
||
size_t | iv_len, |
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const unsigned char * | add, |
||
size_t | add_len, |
||
const unsigned char * | tag, |
||
size_t | tag_len, |
||
const unsigned char * | input, |
||
unsigned char * | output |
||
) |
This function performs a GCM authenticated decryption of a buffer.
- Note
- For decryption, the output buffer cannot be the same as input buffer. If the buffers overlap, the output buffer must trail at least 8 Bytes behind the input buffer.
- Parameters
-
ctx
The GCM context. length
The length of the ciphertext to decrypt, which is also the length of the decrypted plaintext. iv
The initialization vector. iv_len
The length of the IV. add
The buffer holding the additional data. add_len
The length of the additional data. tag
The buffer holding the tag to verify. tag_len
The length of the tag to verify. input
The buffer holding the ciphertext. Its size is length. output
The buffer for holding the decrypted plaintext. It must have room for length bytes.
- Returns
0
if successful and authenticated.- MBEDTLS_ERR_GCM_AUTH_FAILED if the tag does not match.
- MBEDTLS_ERR_GCM_BAD_INPUT if the lengths are not valid.
- MBEDTLS_ERR_GCM_HW_ACCEL_FAILED or a cipher-specific error code if the decryption failed.
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 |
||
) |
This function performs GCM encryption or decryption of a buffer.
- Note
- For encryption, the output buffer can be the same as the input buffer. For decryption, the output buffer cannot be the same as input buffer. If the buffers overlap, the output buffer must trail at least 8 Bytes behind the input buffer.
- Warning
- When this function performs a decryption, it outputs the authentication tag and does not verify that the data is authentic. You should use this function to perform encryption only. For decryption, use mbedtls_gcm_auth_decrypt() instead.
- Parameters
-
ctx
The GCM context to use for encryption or decryption. mode
The operation to perform: - MBEDTLS_GCM_ENCRYPT to perform authenticated encryption. The ciphertext is written to
output
and the authentication tag is written totag
. - MBEDTLS_GCM_DECRYPT to perform decryption. The plaintext is written to
output
and the authentication tag is written totag
. Note that this mode is not recommended, because it does not verify the authenticity of the data. For this reason, you should use mbedtls_gcm_auth_decrypt() instead of calling this function in decryption mode.
length
The length of the input data, which is equal to the length of the output data. iv
The initialization vector. iv_len
The length of the IV. add
The buffer holding the additional data. add_len
The length of the additional data. input
The buffer holding the input data. Its size is length. output
The buffer for holding the output data. It must have room for length bytes. tag_len
The length of the tag to generate. tag
The buffer for holding the tag. - MBEDTLS_GCM_ENCRYPT to perform authenticated encryption. The ciphertext is written to
- Returns
0
if the encryption or decryption was performed successfully. Note that in MBEDTLS_GCM_DECRYPT mode, this does not indicate that the data is authentic.- MBEDTLS_ERR_GCM_BAD_INPUT if the lengths are not valid.
- MBEDTLS_ERR_GCM_HW_ACCEL_FAILED or a cipher-specific error code if the encryption or decryption failed.
int mbedtls_gcm_finish | ( | mbedtls_gcm_context * | ctx, |
unsigned char * | tag, |
||
size_t | tag_len |
||
) |
This function finishes the GCM operation and generates the authentication tag.
It wraps up the GCM stream, and generates the tag. The tag can have a maximum length of 16 Bytes.
- Parameters
-
ctx
The GCM context. tag
The buffer for holding the tag. tag_len
The length of the tag to generate. Must be at least four.
- Returns
0
on success, or MBEDTLS_ERR_GCM_BAD_INPUT on failure.
void mbedtls_gcm_free | ( | mbedtls_gcm_context * | ctx | ) |
This function clears a GCM context and the underlying cipher sub-context.
- Parameters
-
ctx
The GCM context to clear.
void mbedtls_gcm_init | ( | mbedtls_gcm_context * | ctx | ) |
This function initializes the specified GCM context, to make references valid, and prepares the context for mbedtls_gcm_setkey() or mbedtls_gcm_free().
The function does not bind the GCM context to a particular cipher, nor set the key. For this purpose, use mbedtls_gcm_setkey().
- Parameters
-
ctx
The GCM context to initialize.
int mbedtls_gcm_setkey | ( | mbedtls_gcm_context * | ctx, |
mbedtls_cipher_id_t |
cipher, |
||
const unsigned char * | key, |
||
unsigned int | keybits |
||
) |
This function associates a GCM context with a cipher algorithm and a key.
- Parameters
-
ctx
The GCM context to initialize. cipher
The 128-bit block cipher to use. key
The encryption key. keybits
The key size in bits. Valid options are: - 128 bits
- 192 bits
- 256 bits
- Returns
0
on success, or a cipher specific error code.
int mbedtls_gcm_starts | ( | mbedtls_gcm_context * | ctx, |
int | mode, |
||
const unsigned char * | iv, |
||
size_t | iv_len, |
||
const unsigned char * | add, |
||
size_t | add_len |
||
) |
This function starts a GCM encryption or decryption operation.
- Parameters
-
ctx
The GCM context. mode
The operation to perform: MBEDTLS_GCM_ENCRYPT or MBEDTLS_GCM_DECRYPT. iv
The initialization vector. iv_len
The length of the IV. add
The buffer holding the additional data, or NULL if add_len
is 0.add_len
The length of the additional data. If 0, add
is NULL.
- Returns
0
on success.
int mbedtls_gcm_update | ( | mbedtls_gcm_context * | ctx, |
size_t | length, |
||
const unsigned char * | input, |
||
unsigned char * | output |
||
) |
This function feeds an input buffer into an ongoing GCM encryption or decryption operation.
` The function expects input to be a multiple of 16 Bytes. Only the last call before calling mbedtls_gcm_finish() can be less than 16 Bytes.
- Note
- For decryption, the output buffer cannot be the same as input buffer. If the buffers overlap, the output buffer must trail at least 8 Bytes behind the input buffer.
- Parameters
-
ctx
The GCM context. length
The length of the input data. This must be a multiple of 16 except in the last call before mbedtls_gcm_finish(). input
The buffer holding the input data. output
The buffer for holding the output data.
- Returns
0
on success, or MBEDTLS_ERR_GCM_BAD_INPUT on failure.