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authorEric Biggers <ebiggers@google.com>2017-02-14 13:43:27 -0800
committerHerbert Xu <herbert@gondor.apana.org.au>2017-03-09 18:34:14 +0800
commit63be5b53b6d15f7706ad21e9801dae5b723e8340 (patch)
tree15c06f53c7629d91010e4f3f66830d44f565d220 /include/crypto
parent28b62b1458685d8f68f67d9b2d511bf8fa32b746 (diff)
crypto: gf128mul - fix some comments
Fix incorrect references to GF(128) instead of GF(2^128), as these are two entirely different fields, and fix a few other incorrect comments. Cc: Alex Cope <alexcope@google.com> Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Diffstat (limited to 'include/crypto')
-rw-r--r--include/crypto/gf128mul.h26
1 files changed, 14 insertions, 12 deletions
diff --git a/include/crypto/gf128mul.h b/include/crypto/gf128mul.h
index 592d47e565a8..9662c4538873 100644
--- a/include/crypto/gf128mul.h
+++ b/include/crypto/gf128mul.h
@@ -43,7 +43,7 @@
---------------------------------------------------------------------------
Issue Date: 31/01/2006
- An implementation of field multiplication in Galois Field GF(128)
+ An implementation of field multiplication in Galois Field GF(2^128)
*/
#ifndef _CRYPTO_GF128MUL_H
@@ -65,7 +65,7 @@
* are left and the lsb's are right. char b[16] is an array and b[0] is
* the first octet.
*
- * 80000000 00000000 00000000 00000000 .... 00000000 00000000 00000000
+ * 10000000 00000000 00000000 00000000 .... 00000000 00000000 00000000
* b[0] b[1] b[2] b[3] b[13] b[14] b[15]
*
* Every bit is a coefficient of some power of X. We can store the bits
@@ -85,15 +85,17 @@
* Both of the above formats are easy to implement on big-endian
* machines.
*
- * EME (which is patent encumbered) uses the ble format (bits are stored
- * in big endian order and the bytes in little endian). The above buffer
- * represents X^7 in this case and the primitive polynomial is b[0] = 0x87.
+ * XTS and EME (the latter of which is patent encumbered) use the ble
+ * format (bits are stored in big endian order and the bytes in little
+ * endian). The above buffer represents X^7 in this case and the
+ * primitive polynomial is b[0] = 0x87.
*
* The common machine word-size is smaller than 128 bits, so to make
* an efficient implementation we must split into machine word sizes.
- * This file uses one 32bit for the moment. Machine endianness comes into
- * play. The lle format in relation to machine endianness is discussed
- * below by the original author of gf128mul Dr Brian Gladman.
+ * This implementation uses 64-bit words for the moment. Machine
+ * endianness comes into play. The lle format in relation to machine
+ * endianness is discussed below by the original author of gf128mul Dr
+ * Brian Gladman.
*
* Let's look at the bbe and ble format on a little endian machine.
*
@@ -127,10 +129,10 @@
* machines this will automatically aligned to wordsize and on a 64-bit
* machine also.
*/
-/* Multiply a GF128 field element by x. Field elements are held in arrays
- of bytes in which field bits 8n..8n + 7 are held in byte[n], with lower
- indexed bits placed in the more numerically significant bit positions
- within bytes.
+/* Multiply a GF(2^128) field element by x. Field elements are
+ held in arrays of bytes in which field bits 8n..8n + 7 are held in
+ byte[n], with lower indexed bits placed in the more numerically
+ significant bit positions within bytes.
On little endian machines the bit indexes translate into the bit
positions within four 32-bit words in the following way