interop/crypto: update documentation

pkg/interop/crypto/crypto.go

@@ -1,14 +1,15 @@
+/*
+Package crypto provides an interface to cryptographic syscalls.
+*/
 package crypto
 
-// Package crypto provides function signatures that can be used inside
+// SHA256 computes SHA256 hash of b. It uses `Neo.Crypto.SHA256` syscall.
-// smart contracts that are written in the neo-go framework.
-
-// SHA256 computes the sha256 hash of b.
 func SHA256(b []byte) []byte {
 	return nil
 }
 
-// ECDsaVerify checks that sig is msg's signature with pub.
+// ECDsaVerify checks that sig is correct msg's signature for a given pub
+// (serialized public key). It uses `Neo.Crypto.ECDsaVerify` syscall.
 func ECDsaVerify(msg []byte, pub []byte, sig []byte) bool {
 	return false
 }