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crypto: xchacha20 - fix comments for test vectors

PATCH In review Eric Biggers 2 participants 2 messages Dec 6, 2018 – Dec 13, 2018

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Crypto API Arm STM32
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Eric Biggers

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PATCH 1/1 crypto: xchacha20 - fix comments for test vectors

From: Eric Biggers <[email protected]>

The kernel's ChaCha20 uses the RFC7539 convention of the nonce being 12 bytes rather than 8, so actually I only appended 12 random bytes (not
16) to its test vectors to form 24-byte nonces for the XChaCha20 test vectors. The other 4 bytes were just from zero-padding the stream position to 8 bytes. Fix the comments above the test vectors.

Signed-off-by Eric Biggers <[email protected]>
---
 crypto/testmgr.h | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)
crypto/testmgr.h +6 -8
index 357cf4cbcbb1c..e8f47d7b92cdd 100644
@@ -32281,8 +32281,9 @@ static const struct cipher_testvec xchacha20_tv_template[] = {
 			  "\x57\x78\x8e\x6f\xae\x90\xfc\x31"
 			  "\x09\x7c\xfc",
 		.len	= 91,
-	}, { /* Taken from the ChaCha20 test vectors, appended 16 random bytes
-		to nonce, and recomputed the ciphertext with libsodium */
+	}, { /* Taken from the ChaCha20 test vectors, appended 12 random bytes
+		to the nonce, zero-padded the stream position from 4 to 8 bytes,
+		and recomputed the ciphertext using libsodium's XChaCha20 */
 		.key	= "\x00\x00\x00\x00\x00\x00\x00\x00"
 			  "\x00\x00\x00\x00\x00\x00\x00\x00"
 			  "\x00\x00\x00\x00\x00\x00\x00\x00"

@@ -32309,8 +32310,7 @@ static const struct cipher_testvec xchacha20_tv_template[] = {
 			  "\x03\xdc\xf8\x2b\xc1\xe1\x75\x67"
 			  "\x23\x7b\xe6\xfc\xd4\x03\x86\x54",
 		.len	= 64,
-	}, { /* Taken from the ChaCha20 test vectors, appended 16 random bytes
-		to nonce, and recomputed the ciphertext with libsodium */
+	}, { /* Derived from a ChaCha20 test vector, via the process above */
 		.key	= "\x00\x00\x00\x00\x00\x00\x00\x00"
 			  "\x00\x00\x00\x00\x00\x00\x00\x00"
 			  "\x00\x00\x00\x00\x00\x00\x00\x00"

@@ -32419,8 +32419,7 @@ static const struct cipher_testvec xchacha20_tv_template[] = {
 		.np	= 3,
 		.tap	= { 375 - 20, 4, 16 },
 
-	}, { /* Taken from the ChaCha20 test vectors, appended 16 random bytes
-		to nonce, and recomputed the ciphertext with libsodium */
+	}, { /* Derived from a ChaCha20 test vector, via the process above */
 		.key	= "\x1c\x92\x40\xa5\xeb\x55\xd3\x8a"
 			  "\xf3\x33\x88\x86\x04\xf6\xb5\xf0"
 			  "\x47\x39\x17\xc1\x40\x2b\x80\x09"

@@ -32463,8 +32462,7 @@ static const struct cipher_testvec xchacha20_tv_template[] = {
 			  "\x65\x03\xfa\x45\xf7\x9e\x53\x7a"
 			  "\x99\xf1\x82\x25\x4f\x8d\x07",
 		.len	= 127,
-	}, { /* Taken from the ChaCha20 test vectors, appended 16 random bytes
-		to nonce, and recomputed the ciphertext with libsodium */
+	}, { /* Derived from a ChaCha20 test vector, via the process above */
 		.key	= "\x1c\x92\x40\xa5\xeb\x55\xd3\x8a"
 			  "\xf3\x33\x88\x86\x04\xf6\xb5\xf0"
 			  "\x47\x39\x17\xc1\x40\x2b\x80\x09"
Signature · 1 line
2.20.0.rc2.403.gdbc3b29805-goog
maintainer
#1 lore raw
Quoted 8 lines · Eric Biggers

From: Eric Biggers <[email protected]>

The kernel's ChaCha20 uses the RFC7539 convention of the nonce being 12 bytes rather than 8, so actually I only appended 12 random bytes (not
16) to its test vectors to form 24-byte nonces for the XChaCha20 test vectors. The other 4 bytes were just from zero-padding the stream position to 8 bytes. Fix the comments above the test vectors.

Quoted 4 lines
Signed-off-by Eric Biggers <[email protected]>

---
crypto/testmgr.h | 14 ++++++--------

1 file changed, 6 insertions(+), 8 deletions(-)

Patch applied. Thanks.

Signature · 3 lines
Email: Herbert Xu <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt