On 2026-07-14 13:45, Ilya Leoshkevich wrote:
On 7/10/26 17:28, Harald Freudenberger wrote:
Add a new file crypto/aes-helpers.c with simple functions
to support some AES modes:
- AES cbc: AES_cbc_encrypt() AES_cbc_decrypt()
- AES ctr: AES_ctr_encrypt()
- AES xts: AES_xts_encrypt() AES_xts_decrypt()
and some AES related helpers:
- AES_xor()
- AES_xts_prep_next_tweak()
Add header file include/crypto/aes-helpers.h for these functions
Signed-off-by: Harald Freudenberger <[email protected]>
Reviewed-by: Finn Callies <[email protected]>
---
crypto/aes-helpers.c | 106 ++++++++++++++++++++++++++++++++
crypto/meson.build | 1 +
include/crypto/aes-helpers.h | 116
+++++++++++++++++++++++++++++++++++
3 files changed, 223 insertions(+)
create mode 100644 crypto/aes-helpers.c
create mode 100644 include/crypto/aes-helpers.h
diff --git a/crypto/aes-helpers.c b/crypto/aes-helpers.c
new file mode 100644
index 0000000000..ff4aa0a385
--- /dev/null
+++ b/crypto/aes-helpers.c
[...]
+void AES_ctr_encrypt(const unsigned char *in, unsigned char *out,
+ const unsigned char *ctr, const AES_KEY *key)
+{
+ unsigned char buf[AES_BLOCK_SIZE];
+
+ /* encrypt ctr => buf */
+ AES_encrypt(ctr, buf, key);
+ /* exor input data with encrypted ctr => out */
+ AES_xor(in, buf, out);
+}
+
+/*
+ * Tweak calculation for AES XTS.
+ * Multiply tweak by α (x) in GF(2^128) per IEEE 1619-2007. The tweak
+ * is a 128-bit little-endian integer (tweak[0]=LSB, tweak[15]=MSB).
+ * This implementation has been verified on litte and big endian.
+ */
Nit: do we need to have this comment twice?
It's already present in the header.
Well the text is different. aes-helpers.h:
/**
* AES_xts_prep_next_tweak:
*
* Tweak calculation for AES XTS.
* Prepares the next tweak value for AES-XTS mode by multiplying
* the current tweak by α (x) in GF(2^128) according to IEEE
1619-2007.
*
* @tweak: pointer to tweak value to be updated (16 bytes buffer
* containing a 128 bit little endian integer)
*/
void AES_xts_prep_next_tweak(unsigned char *tweak);
aes-helpers.c:
/*
* Tweak calculation for AES XTS.
* Multiply tweak by α (x) in GF(2^128) per IEEE 1619-2007. The tweak
* is a 128-bit little-endian integer (tweak[0]=LSB, tweak[15]=MSB).
* This implementation has been verified on little and big endian.
*/
void AES_xts_prep_next_tweak(unsigned char *tweak)
And the idea was to describe in the header more the usage whereas
in the c code describe the implementation.
Also typo: litte -> little (but I'm not sure if we even need to state
that in the code).
fixed the typo -> see v13
[...]
Reviewed-by: Ilya Leoshkevich <[email protected]>
Thanks for your review
