Added some utils methods

CryptoExchange.Net/Authentication/AuthenticationProvider.cs

@@ -442,6 +442,14 @@ namespace CryptoExchange.Net.Authentication
         /// <param name="buff"></param>
         /// <returns></returns>
         protected static string BytesToHexString(byte[] buff)
+            => BytesToHexString(new ArraySegment<byte>(buff));
+
+        /// <summary>
+        /// Convert byte array to hex string
+        /// </summary>
+        /// <param name="buff"></param>
+        /// <returns></returns>
+        protected static string BytesToHexString(ArraySegment<byte> buff)
         {
 #if NET9_0_OR_GREATER
             return Convert.ToHexString(buff);
@@ -453,6 +461,26 @@ namespace CryptoExchange.Net.Authentication
 #endif
         }
 
+        /// <summary>
+        /// Convert a hex encoded string to byte array
+        /// </summary>
+        /// <param name="hexString"></param>
+        /// <returns></returns>
+        protected static byte[] HexToBytesString(string hexString)
+        {
+            if (hexString.StartsWith("0x"))
+                hexString = hexString.Substring(2);
+
+            byte[] bytes = new byte[hexString.Length / 2];
+            for (int i = 0; i < hexString.Length; i += 2)
+            {
+                string hexSubstring = hexString.Substring(i, 2);
+                bytes[i / 2] = Convert.ToByte(hexSubstring, 16);
+            }
+
+            return bytes;
+        }
+
         /// <summary>
         /// Convert byte array to base64 string
         /// </summary>

CryptoExchange.Net/ExchangeHelpers.cs

@@ -242,8 +242,7 @@ namespace CryptoExchange.Net
         /// <summary>
         /// Generate a long value
         /// </summary>
-        /// <param name="maxLength">Max character length</param>
+        /// <param name="maxLength">Max number of digits</param>
-        /// <returns></returns>
         public static long RandomLong(int maxLength)
         {
 #if NETSTANDARD2_1_OR_GREATER || NET9_0_OR_GREATER
@@ -259,6 +258,19 @@ namespace CryptoExchange.Net
                 return value;
         }
 
+        public static long RandomLong(long minValue, long maxValue)
+        {
+#if NET8_0_OR_GREATER
+            var buf = RandomNumberGenerator.GetBytes(8);
+#else
+            byte[] buf = new byte[8];
+            var random = new Random();
+            random.NextBytes(buf);
+#endif
+            long longRand = BitConverter.ToInt64(buf, 0);
+            return (Math.Abs(longRand % (maxValue - minValue)) + minValue);
+        }
+
         /// <summary>
         /// Generate a random string of specified length
         /// </summary>