interop/crypto: update documentation

pkg/interop/crypto/crypto.go

@@ -1,29 +1,32 @@
+/*
+Package crypto provides an interface to VM cryptographic instructions.
+*/
 package crypto
 
-// Package crypto provides function signatures that can be used inside
+// SHA1 computes SHA1 hash of b. It uses `SHA1` VM instruction.
-// smart contracts that are written in the neo-go framework.
-
-// SHA1 computes the sha1 hash of b.
 func SHA1(b []byte) []byte {
 	return nil
 }
 
-// SHA256 computes the sha256 hash of b.
+// SHA256 computes SHA256 hash of b. It uses `SHA256` VM instruction.
 func SHA256(b []byte) []byte {
 	return nil
 }
 
-// Hash160 computes the sha256 + ripemd160 of b.
+// Hash160 computes SHA256 + RIPEMD-160 of b, which is commonly used for
+// script hashing and address generation. It uses `HASH160` VM instruction.
 func Hash160(b []byte) []byte {
 	return nil
 }
 
-// Hash256 computes the sha256^2 hash of b.
+// Hash256 computes double SHA256 hash of b (SHA256(SHA256(b))) which is used
+// as ID for transactions, blocks and assets. It uses `HASH256` VM instruction.
 func Hash256(b []byte) []byte {
 	return nil
 }
 
-// VerifySignature checks that sig is msg's signature with pub.
+// VerifySignature checks that sig is correct msg's signature for a given pub
+// (serialized public key). It uses `VERIFY` VM instruction.
 func VerifySignature(msg []byte, sig []byte, pub []byte) bool {
 	return false
 }