move cryptography to its own folder/files

pkg/cryptography/constants.go

@@ -0,0 +1,22 @@
+package cryptography
+
+import (
+	"crypto/sha256"
+
+	"golang.org/x/crypto/curve25519"
+)
+
+const (
+	SHA256Size = 32
+)
+
+// GetBasepoint returns the standard Curve25519 basepoint
+func GetBasepoint() []byte {
+	return curve25519.Basepoint
+}
+
+func Hash(data []byte) []byte {
+	h := sha256.New()
+	h.Write(data)
+	return h.Sum(nil)
+}