Commit 8dfa20fc authored by Eric Biggers's avatar Eric Biggers Committed by Herbert Xu

crypto: ghash - add comment and improve help text

To help avoid confusion, add a comment to ghash-generic.c which explains
the convention that the kernel's implementation of GHASH uses.

Also update the Kconfig help text and module descriptions to call GHASH
a "hash function" rather than a "message digest", since the latter
normally means a real cryptographic hash function, which GHASH is not.

Cc: Pascal Van Leeuwen <pvanleeuwen@verimatrix.com>
Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Reviewed-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: default avatarPascal Van Leeuwen <pvanleeuwen@verimatrix.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent 065cf577
...@@ -18,7 +18,7 @@ ...@@ -18,7 +18,7 @@
#include <linux/crypto.h> #include <linux/crypto.h>
#include <linux/module.h> #include <linux/module.h>
MODULE_DESCRIPTION("GHASH secure hash using ARMv8 Crypto Extensions"); MODULE_DESCRIPTION("GHASH hash function using ARMv8 Crypto Extensions");
MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>"); MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
MODULE_LICENSE("GPL v2"); MODULE_LICENSE("GPL v2");
MODULE_ALIAS_CRYPTO("ghash"); MODULE_ALIAS_CRYPTO("ghash");
......
...@@ -153,4 +153,4 @@ module_exit(ghash_mod_exit); ...@@ -153,4 +153,4 @@ module_exit(ghash_mod_exit);
MODULE_ALIAS_CRYPTO("ghash"); MODULE_ALIAS_CRYPTO("ghash");
MODULE_LICENSE("GPL"); MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("GHASH Message Digest Algorithm, s390 implementation"); MODULE_DESCRIPTION("GHASH hash function, s390 implementation");
...@@ -357,6 +357,5 @@ module_init(ghash_pclmulqdqni_mod_init); ...@@ -357,6 +357,5 @@ module_init(ghash_pclmulqdqni_mod_init);
module_exit(ghash_pclmulqdqni_mod_exit); module_exit(ghash_pclmulqdqni_mod_exit);
MODULE_LICENSE("GPL"); MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("GHASH Message Digest Algorithm, " MODULE_DESCRIPTION("GHASH hash function, accelerated by PCLMULQDQ-NI");
"accelerated by PCLMULQDQ-NI");
MODULE_ALIAS_CRYPTO("ghash"); MODULE_ALIAS_CRYPTO("ghash");
...@@ -647,11 +647,12 @@ config CRYPTO_VPMSUM_TESTER ...@@ -647,11 +647,12 @@ config CRYPTO_VPMSUM_TESTER
Unless you are testing these algorithms, you don't need this. Unless you are testing these algorithms, you don't need this.
config CRYPTO_GHASH config CRYPTO_GHASH
tristate "GHASH digest algorithm" tristate "GHASH hash function"
select CRYPTO_GF128MUL select CRYPTO_GF128MUL
select CRYPTO_HASH select CRYPTO_HASH
help help
GHASH is message digest algorithm for GCM (Galois/Counter Mode). GHASH is the hash function used in GCM (Galois/Counter Mode).
It is not a general-purpose cryptographic hash function.
config CRYPTO_POLY1305 config CRYPTO_POLY1305
tristate "Poly1305 authenticator algorithm" tristate "Poly1305 authenticator algorithm"
...@@ -976,12 +977,12 @@ config CRYPTO_WP512 ...@@ -976,12 +977,12 @@ config CRYPTO_WP512
<http://www.larc.usp.br/~pbarreto/WhirlpoolPage.html> <http://www.larc.usp.br/~pbarreto/WhirlpoolPage.html>
config CRYPTO_GHASH_CLMUL_NI_INTEL config CRYPTO_GHASH_CLMUL_NI_INTEL
tristate "GHASH digest algorithm (CLMUL-NI accelerated)" tristate "GHASH hash function (CLMUL-NI accelerated)"
depends on X86 && 64BIT depends on X86 && 64BIT
select CRYPTO_CRYPTD select CRYPTO_CRYPTD
help help
GHASH is message digest algorithm for GCM (Galois/Counter Mode). This is the x86_64 CLMUL-NI accelerated implementation of
The implementation is accelerated by CLMUL-NI of Intel. GHASH, the hash function used in GCM (Galois/Counter mode).
comment "Ciphers" comment "Ciphers"
......
// SPDX-License-Identifier: GPL-2.0-only // SPDX-License-Identifier: GPL-2.0-only
/* /*
* GHASH: digest algorithm for GCM (Galois/Counter Mode). * GHASH: hash function for GCM (Galois/Counter Mode).
* *
* Copyright (c) 2007 Nokia Siemens Networks - Mikko Herranen <mh1@iki.fi> * Copyright (c) 2007 Nokia Siemens Networks - Mikko Herranen <mh1@iki.fi>
* Copyright (c) 2009 Intel Corp. * Copyright (c) 2009 Intel Corp.
* Author: Huang Ying <ying.huang@intel.com> * Author: Huang Ying <ying.huang@intel.com>
*/
/*
* GHASH is a keyed hash function used in GCM authentication tag generation.
*
* The original GCM paper [1] presents GHASH as a function GHASH(H, A, C) which
* takes a 16-byte hash key H, additional authenticated data A, and a ciphertext
* C. It formats A and C into a single byte string X, interprets X as a
* polynomial over GF(2^128), and evaluates this polynomial at the point H.
*
* However, the NIST standard for GCM [2] presents GHASH as GHASH(H, X) where X
* is the already-formatted byte string containing both A and C.
*
* "ghash" in the Linux crypto API uses the 'X' (pre-formatted) convention,
* since the API supports only a single data stream per hash. Thus, the
* formatting of 'A' and 'C' is done in the "gcm" template, not in "ghash".
*
* The reason "ghash" is separate from "gcm" is to allow "gcm" to use an
* accelerated "ghash" when a standalone accelerated "gcm(aes)" is unavailable.
* It is generally inappropriate to use "ghash" for other purposes, since it is
* an "ε-almost-XOR-universal hash function", not a cryptographic hash function.
* It can only be used securely in crypto modes specially designed to use it.
* *
* The algorithm implementation is copied from gcm.c. * [1] The Galois/Counter Mode of Operation (GCM)
* (http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.694.695&rep=rep1&type=pdf)
* [2] Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC
* (https://csrc.nist.gov/publications/detail/sp/800-38d/final)
*/ */
#include <crypto/algapi.h> #include <crypto/algapi.h>
...@@ -156,6 +181,6 @@ subsys_initcall(ghash_mod_init); ...@@ -156,6 +181,6 @@ subsys_initcall(ghash_mod_init);
module_exit(ghash_mod_exit); module_exit(ghash_mod_exit);
MODULE_LICENSE("GPL"); MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("GHASH Message Digest Algorithm"); MODULE_DESCRIPTION("GHASH hash function");
MODULE_ALIAS_CRYPTO("ghash"); MODULE_ALIAS_CRYPTO("ghash");
MODULE_ALIAS_CRYPTO("ghash-generic"); MODULE_ALIAS_CRYPTO("ghash-generic");
...@@ -189,12 +189,12 @@ config S390_PRNG ...@@ -189,12 +189,12 @@ config S390_PRNG
It is available as of z9. It is available as of z9.
config CRYPTO_GHASH_S390 config CRYPTO_GHASH_S390
tristate "GHASH digest algorithm" tristate "GHASH hash function"
depends on S390 depends on S390
select CRYPTO_HASH select CRYPTO_HASH
help help
This is the s390 hardware accelerated implementation of the This is the s390 hardware accelerated implementation of GHASH,
GHASH message digest algorithm for GCM (Galois/Counter Mode). the hash function used in GCM (Galois/Counter mode).
It is available as of z196. It is available as of z196.
......
/* SPDX-License-Identifier: GPL-2.0 */ /* SPDX-License-Identifier: GPL-2.0 */
/* /*
* Common values for GHASH algorithms * Common values for the GHASH hash function
*/ */
#ifndef __CRYPTO_GHASH_H__ #ifndef __CRYPTO_GHASH_H__
......
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