Simplify and rename hash functions

pkg/tlog/tl.go

@@ -7,7 +7,6 @@ import (
 	"crypto/x509"
 	"crypto/x509/pkix"
 	"encoding/base64"
-	"encoding/hex"
 	"encoding/pem"
 	"fmt"
 	"math/big"
@@ -214,7 +213,7 @@ func (tl *RekorTL) VerifyEntryPayload(entryBytes, payload, publicKey []byte) err
 	}
 
 	// compare payload hashes
-	payloadHash := hex.EncodeToString(util.S256(payload))
+	payloadHash := util.SHA256Hex(payload)
 	if rekord.Hash != payloadHash {
 		return fmt.Errorf("error payload and tl entry hash mismatch")
 	}

pkg/tlog/tl_test.go

@@ -44,7 +44,7 @@ func TestCreateX509Cert(t *testing.T) {
 func TestUploadAndVerifyLogEntry(t *testing.T) {
 	// message digest
 	payload := []byte("test")
-	hash := util.S256(payload)
+	hash := util.SHA256(payload)
 
 	// generate ephemeral keys to sign message digest
 	signer, err := signerverifier.GenKeyPair()