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[rng] Choose HMAC_DRBG using SHA-256 as the DRBG algorithm 

Both HMAC_DRBG using SHA-1 and HMAC_DRBG using SHA-256 are Approved
algorithms in ANS X9.82 for our chosen security strength of 128 bits.
However, general recommendations (see e.g. NIST SP800-57) are to use a
larger hash function in preference to SHA-1.

Since SHA-256 is required anyway for TLSv1.2 support, there is no code
size penalty for switching HMAC_DRBG to also use SHA-256.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
pull/6/head
Michael Brown 2012-03-06 13:42:06 +00:00
parent a810258b42
commit 8d038040ea
1 changed files with 6 additions and 7 deletions
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13
src/include/ipxe/drbg.h
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@ -10,14 +10,14 @@
FILE_LICENCE ( GPL2_OR_LATER );
#include <stdint.h>
#include <ipxe/sha1.h>
#include <ipxe/sha256.h>
#include <ipxe/hmac_drbg.h>
/** Choose HMAC_DRBG using SHA-1
/** Choose HMAC_DRBG using SHA-256
*
* HMAC_DRBG using SHA-1 is an Approved algorithm in ANS X9.82.
* HMAC_DRBG using SHA-256 is an Approved algorithm in ANS X9.82.
*/
#define HMAC_DRBG_ALGORITHM HMAC_DRBG_SHA1
#define HMAC_DRBG_ALGORITHM HMAC_DRBG_SHA256
/** Maximum security strength */
#define DRBG_MAX_SECURITY_STRENGTH \
@ -25,10 +25,9 @@ FILE_LICENCE ( GPL2_OR_LATER );
/** Security strength
*
* We choose to operate at the maximum security strength supported by
* the algorithm.
* We choose to operate at a strength of 128 bits.
*/
#define DRBG_SECURITY_STRENGTH DRBG_MAX_SECURITY_STRENGTH
#define DRBG_SECURITY_STRENGTH 128
/** Minimum entropy input length */
#define DRBG_MIN_ENTROPY_LEN_BYTES \