RSA: Implement signature verification algorithm [PKCS#1 / RFC3447]

Implement RSA public key cryptography [PKCS#1 / RFC3447].  At this time, only
the signature verification algorithm is supported.  This uses the asymmetric
public key subtype to hold its key data.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/crypto/asymmetric_keys/Makefile b/crypto/asymmetric_keys/Makefile
index 8dcdf0c..7c92691 100644
--- a/crypto/asymmetric_keys/Makefile
+++ b/crypto/asymmetric_keys/Makefile
@@ -7,3 +7,4 @@
 asymmetric_keys-y := asymmetric_type.o signature.o
 
 obj-$(CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE) += public_key.o
+obj-$(CONFIG_PUBLIC_KEY_ALGO_RSA) += rsa.o