From 8d038040eaac85bbe08f0b5ba507ff0167b3a2f3 Mon Sep 17 00:00:00 2001 From: Michael Brown Date: Tue, 6 Mar 2012 13:42:06 +0000 Subject: [PATCH] [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 --- src/include/ipxe/drbg.h | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) diff --git a/src/include/ipxe/drbg.h b/src/include/ipxe/drbg.h index 139f03c54..6374e7787 100644 --- a/src/include/ipxe/drbg.h +++ b/src/include/ipxe/drbg.h @@ -10,14 +10,14 @@ FILE_LICENCE ( GPL2_OR_LATER ); #include -#include +#include #include -/** 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 \