Data commit

Task/Bitcoin-address-validation/C-sharp/bitcoin-address-validation.cs

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+using System;
+using System.Linq;
+using System.Security.Cryptography;
+using NUnit.Framework;
+
+namespace BitcoinValidator
+{
+    public class ValidateTest
+    {
+        [TestCase]
+        public void ValidateBitcoinAddressTest()
+        {
+            Assert.IsTrue(ValidateBitcoinAddress("1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i")); // VALID
+            Assert.IsTrue(ValidateBitcoinAddress("1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nK9")); // VALID
+            Assert.Throws<Exception>(() => ValidateBitcoinAddress("1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62X")); // checksum changed, original data
+            Assert.Throws<Exception>(() => ValidateBitcoinAddress("1ANNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i")); // data changed, original checksum
+            Assert.Throws<Exception>(() => ValidateBitcoinAddress("1A Na15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i")); // invalid chars
+            Assert.Throws<Exception>(() => ValidateBitcoinAddress("BZbvjr")); // checksum is fine, address too short
+        }
+
+        public static bool ValidateBitcoinAddress(string address)
+        {
+            if (address.Length < 26 || address.Length > 35) throw new Exception("wrong length");
+            var decoded = DecodeBase58(address);
+            var d1 = Hash(decoded.SubArray(0, 21));
+            var d2 = Hash(d1);
+            if (!decoded.SubArray(21, 4).SequenceEqual(d2.SubArray(0, 4))) throw new Exception("bad digest");
+            return true;
+        }
+
+        const string Alphabet = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
+        const int Size = 25;
+
+        private static byte[] DecodeBase58(string input)
+        {
+            var output = new byte[Size];
+            foreach (var t in input)
+            {
+                var p = Alphabet.IndexOf(t);
+                if (p == -1) throw new Exception("invalid character found");
+                var j = Size;
+                while (--j > 0)
+                {
+                    p += 58 * output[j];
+                    output[j] = (byte)(p % 256);
+                    p /= 256;
+                }
+                if (p != 0) throw new Exception("address too long");
+            }
+            return output;
+        }
+
+        private static byte[] Hash(byte[] bytes)
+        {
+            var hasher = new SHA256Managed();
+            return hasher.ComputeHash(bytes);
+        }
+    }
+
+    public static class ArrayExtensions
+    {
+        public static T[] SubArray<T>(this T[] data, int index, int length)
+        {
+            var result = new T[length];
+            Array.Copy(data, index, result, 0, length);
+            return result;
+        }
+    }
+}