[CRYPTO] seqiv: Add Sequence Number IV Generator

This generator generates an IV based on a sequence number by xoring it
with a salt.  This algorithm is mainly useful for CTR and similar modes.

This patch also sets it as the default IV generator for ctr.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
diff --git a/crypto/Kconfig b/crypto/Kconfig
index c4b6c91..7ad9711 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -32,6 +32,14 @@
 	tristate
 	select CRYPTO_ALGAPI
 
+config CRYPTO_SEQIV
+	tristate "Sequence Number IV Generator"
+	select CRYPTO_BLKCIPHER
+	help
+	  This IV generator generates an IV based on a sequence number by
+	  xoring it with a salt.  This algorithm is mainly useful for CTR
+	  and similar modes.
+
 config CRYPTO_HASH
 	tristate
 	select CRYPTO_ALGAPI
@@ -197,6 +205,7 @@
 config CRYPTO_CTR
 	tristate "CTR support"
 	select CRYPTO_BLKCIPHER
+	select CRYPTO_SEQIV
 	select CRYPTO_MANAGER
 	help
 	  CTR: Counter mode