Added crypto file

CryptographyService.cs

@@ -0,0 +1,46 @@
+using System;
+using Sodium;
+
+namespace TeleTok
+{
+    public class CryptographyService
+    {
+        public string ToHexString(byte[] input)
+        {
+            var hexString = BitConverter.ToString(input);
+
+            string result = hexString.Replace("-", "");
+
+            return result.ToLower();
+        }
+
+        public byte[] GenerateLoginDigest()
+        {
+            long now = DateTimeOffset.UtcNow.ToUnixTimeSeconds() * 1000;
+            var message = $"login:{now / 1000 / (5 * 60)}";
+
+            return GenericHash.Hash(message, (byte[]?) null, 32);
+        }
+
+        public KeyPair GenerateEd25519KeyPair(string seed)
+        {
+            byte[] hash = GenericHash.Hash(seed, (byte[]?) null, 32);
+
+            return PublicKeyAuth.GenerateKeyPair(hash);
+        }
+
+        public string GenerateHexSignature(byte[] loginDigest, byte[] secretKey)
+        {
+            byte[] signature = PublicKeyAuth.SignDetached(loginDigest, secretKey);
+
+            return ToHexString(signature);
+        }
+
+        public string GenerateHexId(byte[] publicKey)
+        {
+            byte[] hash = GenericHash.Hash(publicKey, null, publicKey.Length);
+
+            return ToHexString(hash);
+        }
+    }
+}