From 355912852115cd8aa4ad02c25182ae615ce925fb Mon Sep 17 00:00:00 2001 From: Stephan Mueller Date: Tue, 14 Jun 2016 07:34:13 +0200 Subject: crypto: drbg - use CTR AES instead of ECB AES The CTR DRBG derives its random data from the CTR that is encrypted with AES. This patch now changes the CTR DRBG implementation such that the CTR AES mode is employed. This allows the use of steamlined CTR AES implementation such as ctr-aes-aesni. Unfortunately there are the following subtile changes we need to apply when using the CTR AES mode: - the CTR mode increments the counter after the cipher operation, but the CTR DRBG requires the increment before the cipher op. Hence, the crypto_inc is applied to the counter (drbg->V) once it is recalculated. - the CTR mode wants to encrypt data, but the CTR DRBG is interested in the encrypted counter only. The full CTR mode is the XOR of the encrypted counter with the plaintext data. To access the encrypted counter, the patch uses a NULL data vector as plaintext to be "encrypted". Signed-off-by: Stephan Mueller Signed-off-by: Herbert Xu --- crypto/Kconfig | 1 + 1 file changed, 1 insertion(+) (limited to 'crypto/Kconfig') diff --git a/crypto/Kconfig b/crypto/Kconfig index 1d33beb6a1ae..c903f1832f2c 100644 --- a/crypto/Kconfig +++ b/crypto/Kconfig @@ -1567,6 +1567,7 @@ config CRYPTO_DRBG_HASH config CRYPTO_DRBG_CTR bool "Enable CTR DRBG" select CRYPTO_AES + depends on CRYPTO_CTR help Enable the CTR DRBG variant as defined in NIST SP800-90A. -- cgit v1.2.3-55-g7522