move cryptography to its own folder/files

pkg/cryptography/ed25519.go

@@ -0,0 +1,18 @@
+package cryptography
+
+import (
+	"crypto/ed25519"
+	"crypto/rand"
+)
+
+func GenerateSigningKeyPair() (ed25519.PublicKey, ed25519.PrivateKey, error) {
+	return ed25519.GenerateKey(rand.Reader)
+}
+
+func Sign(privateKey ed25519.PrivateKey, message []byte) []byte {
+	return ed25519.Sign(privateKey, message)
+}
+
+func Verify(publicKey ed25519.PublicKey, message, signature []byte) bool {
+	return ed25519.Verify(publicKey, message, signature)
+}