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Initial untested implementation of deterministic message signing (#37).

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Ken MacKay
2015-06-14 15:13:28 -07:00
parent 46dadf0705
commit c13e915870
2 changed files with 205 additions and 12 deletions
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uECC.h
+83 -4
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@@ -72,7 +72,7 @@ A correctly functioning RNG function must be set (using uECC_set_rng()) before c
uECC_make_key() or uECC_sign().
Setting a correctly functioning RNG function improves the resistance to side-channel attacks
for uECC_shared_secret().
for uECC_shared_secret() and uECC_sign_deterministic().
A correct RNG function is set by default when building for Windows, Linux, or OS X.
If you are building on another POSIX-compliant system that supports /dev/random or /dev/urandom,
@@ -129,8 +129,8 @@ Usage: Compute a hash of the data you wish to sign (SHA-2 is recommended) and pa
this function along with your private key.
Inputs:
private_key - Your private key.
hash - The message hash to sign.
private_key - Your private key.
message_hash - The hash of the message to sign.
Outputs:
signature - Will be filled in with the signature value.
@@ -138,9 +138,88 @@ Outputs:
Returns 1 if the signature generated successfully, 0 if an error occurred.
*/
int uECC_sign(const uint8_t private_key[uECC_BYTES],
const uint8_t hash[uECC_BYTES],
const uint8_t message_hash[uECC_BYTES],
uint8_t signature[uECC_BYTES*2]);
/* Define uECC_HASH_BLOCK_SIZE to the block size in bytes of your hash algorithm
(eg 64 for SHA-256) */
/* #define uECC_HASH_BLOCK_SIZE 64 */
/* Define uECC_HASH_RESULT_SIZE to the output size in bytes of your hash algorithm
(eg 32 for SHA-256) */
/* #define uECC_HASH_RESULT_SIZE 32 */
#if defined(uECC_HASH_BLOCK_SIZE) && defined(uECC_HASH_RESULT_SIZE)
/* uECC_HashContext structure.
This is used to pass in an arbitrary hash function to uECC_sign_deterministic().
The structure will be used for multiple hash computations; each time a new hash
is computed, init_hash() will be called, followed by one or more calls to
update_hash(), and finally a call to finish_hash() to prudoce the resulting hash.
The intention is that you will create a structure that includes uECC_HashContext
followed by any hash-specific data. For example:
typedef struct SHA256_HashContext {
uECC_HashContext uECC;
SHA256_CTX ctx;
} SHA256_HashContext;
void SHA256_init(uECC_HashContext *base) {
SHA256_HashContext *context = (SHA256_HashContext *)base;
SHA256_Init(&context->ctx);
}
void SHA256_update(uECC_HashContext *base,
const uint8_t *message,
unsigned message_size) {
SHA256_HashContext *context = (SHA256_HashContext *)base;
SHA256_Update(&context->ctx, message, message_size);
}
void SHA256_finish(uECC_HashContext *base, uint8_t *hash_result) {
SHA256_HashContext *context = (SHA256_HashContext *)base;
SHA256_Final(hash_result, &context->ctx);
}
... when signing ...
{
SHA256_HashContext ctx = {{&SHA256_init, &SHA256_update, &SHA256_finish}};
uECC_sign_deterministic(key, message_hash, &ctx, signature);
}
*/
typedef struct uECC_HashContext {
void (*init_hash)(struct uECC_HashContext *context);
void (*update_hash)(struct uECC_HashContext *context,
const uint8_t *message,
unsigned message_size);
void (*finish_hash)(struct uECC_HashContext *context, uint8_t *hash_result);
} uECC_HashContext;
/* uECC_sign_deterministic() function.
Generate an ECDSA signature for a given hash value, using a deterministic algorithm
(see RFC 6979). You do not need to set the RNG using uECC_set_rng() before calling
this function; however, if the RNG is defined it will improve resistance to side-channel
attacks.
Usage: Compute a hash of the data you wish to sign (SHA-2 is recommended) and pass it in to
this function along with your private key and a hash context.
Inputs:
private_key - Your private key.
message_hash - The hash of the message to sign.
hash_context - A hash context to use.
Outputs:
signature - Will be filled in with the signature value.
Returns 1 if the signature generated successfully, 0 if an error occurred.
*/
int uECC_sign_deterministic(const uint8_t private_key[uECC_BYTES],
const uint8_t message_hash[uECC_BYTES],
uECC_HashContext *hash_context,
uint8_t signature[uECC_BYTES*2]);
#endif /* defined(uECC_HASH_BLOCK_SIZE) && defined(uECC_HASH_RESULT_SIZE) */
/* uECC_verify() function.
Verify an ECDSA signature.