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Enable multiple XTS encryption or decryption

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multiple xts_encrypt() cannot be performed because the
tweak is not updated. That means that
  xts_encrypt(buffer1, tweak)
  xts_encrypt(buffer2, tweak)
is not the same as
  xts_encrypt(concat(buffer1, buffer2), tweak)

Current patch enables such functionalities by
updating the tweak as output of the encryption.
Note that the tweak is no more constant.

The very same modification is performed
on xts_decrypt()

Signed-off-by: Pascal Brand <pascal.brand@st.com>
This commit is contained in:
Pascal Brand 2014-09-18 01:42:54 +02:00 committed by Steffen Jaeckel
parent 824c7bf16a
commit adc54d08d0
4 changed files with 19 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
src/headers/tomcrypt_cipher.h
View File

@ -884,12 +884,12 @@ int xts_start( int cipher,
int xts_encrypt(
const unsigned char *pt, unsigned long ptlen,
unsigned char *ct,
const unsigned char *tweak,
unsigned char *tweak,
symmetric_xts *xts);
int xts_decrypt(
const unsigned char *ct, unsigned long ptlen,
unsigned char *pt,
const unsigned char *tweak,
unsigned char *tweak,
symmetric_xts *xts);
void xts_done(symmetric_xts *xts);

7
src/modes/xts/xts_decrypt.c
View File

@ -60,7 +60,7 @@ static int tweak_uncrypt(const unsigned char *C, unsigned char *P, unsigned char
*/int xts_decrypt(
const unsigned char *ct, unsigned long ptlen,
unsigned char *pt,
const unsigned char *tweak,
unsigned char *tweak,
symmetric_xts *xts)
{
unsigned char PP[16], CC[16], T[16];
@ -130,6 +130,11 @@ static int tweak_uncrypt(const unsigned char *C, unsigned char *P, unsigned char
}
}
/* Decrypt the tweak back */
if ((err = cipher_descriptor[xts->cipher].ecb_decrypt(T, tweak, &xts->key2)) != CRYPT_OK) {
return err;
}
return CRYPT_OK;
}

7
src/modes/xts/xts_encrypt.c
View File

@ -63,7 +63,7 @@ static int tweak_crypt(const unsigned char *P, unsigned char *C, unsigned char *
int xts_encrypt(
const unsigned char *pt, unsigned long ptlen,
unsigned char *ct,
const unsigned char *tweak,
unsigned char *tweak,
symmetric_xts *xts)
{
unsigned char PP[16], CC[16], T[16];
@ -131,6 +131,11 @@ int xts_encrypt(
}
}
/* Decrypt the tweak back */
if ((err = cipher_descriptor[xts->cipher].ecb_decrypt(T, tweak, &xts->key2)) != CRYPT_OK) {
return err;
}
return err;
}

8
src/modes/xts/xts_test.c
View File

@ -142,7 +142,7 @@ int xts_test(void)
},
};
unsigned char OUT[512], T[16];
unsigned char OUT[512], Torg[16], T[16];
ulong64 seq;
symmetric_xts xts;
int i, err, idx;
@ -161,9 +161,10 @@ int xts_test(void)
}
seq = tests[i].seqnum;
STORE64L(seq,T);
XMEMSET(T+8, 0, 8);
STORE64L(seq,Torg);
XMEMSET(Torg+8, 0, 8);
XMEMCPY(T, Torg, sizeof(T));
err = xts_encrypt(tests[i].PTX, tests[i].PTLEN, OUT, T, &xts);
if (err != CRYPT_OK) {
xts_done(&xts);
@ -175,6 +176,7 @@ int xts_test(void)
return CRYPT_FAIL_TESTVECTOR;
}
XMEMCPY(T, Torg, sizeof(T));
err = xts_decrypt(tests[i].CTX, tests[i].PTLEN, OUT, T, &xts);
if (err != CRYPT_OK) {
xts_done(&xts);