Fix Base58 issues (3x)

neo.UnitTests/Cryptography/UT_Base58.cs

@@ -2,30 +2,49 @@
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using Neo.Cryptography;
 using System;
+using System.Collections.Generic;
 
 namespace Neo.UnitTests.Cryptography
 {
     [TestClass]
     public class UT_Base58
     {
-        byte[] decoded1 = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
-        string encoded1 = "1kA3B2yGe2z4";
-        byte[] decoded2 = { 0, 0, 0, 0, 0 };
-        string encoded2 = "1111";
-
         [TestMethod]
-        public void TestEncode()
+        public void TestEncodeDecode()
         {
-            Base58.Encode(decoded1).Should().Be(encoded1);
-        }
+            var bitcoinTest = new Dictionary<string, string>()
+            {
+                // Tests from https://github.com/bitcoin/bitcoin/blob/46fc4d1a24c88e797d6080336e3828e45e39c3fd/src/test/data/base58_encode_decode.json
 
-        [TestMethod]
-        public void TestDecode()
-        {
-            Base58.Decode(encoded1).Should().BeEquivalentTo(decoded1);
-            Base58.Decode(encoded2).Should().BeEquivalentTo(decoded2);
-            Action action = () => Base58.Decode(encoded1 + "l").Should().BeEquivalentTo(decoded1);
-            action.Should().Throw<FormatException>();
+                {"", ""},
+                {"61", "2g"},
+                {"626262", "a3gV"},
+                {"636363", "aPEr"},
+                {"73696d706c792061206c6f6e6720737472696e67", "2cFupjhnEsSn59qHXstmK2ffpLv2"},
+                {"00eb15231dfceb60925886b67d065299925915aeb172c06647", "1NS17iag9jJgTHD1VXjvLCEnZuQ3rJDE9L"},
+                {"516b6fcd0f", "ABnLTmg"},
+                {"bf4f89001e670274dd", "3SEo3LWLoPntC"},
+                {"572e4794", "3EFU7m"},
+                {"ecac89cad93923c02321", "EJDM8drfXA6uyA"},
+                {"10c8511e", "Rt5zm"},
+                {"00000000000000000000", "1111111111"},
+                {"000111d38e5fc9071ffcd20b4a763cc9ae4f252bb4e48fd66a835e252ada93ff480d6dd43dc62a641155a5", "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"},
+                {"000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f202122232425262728292a2b2c2d2e2f303132333435363738393a3b3c3d3e3f404142434445464748494a4b4c4d4e4f505152535455565758595a5b5c5d5e5f606162636465666768696a6b6c6d6e6f707172737475767778797a7b7c7d7e7f808182838485868788898a8b8c8d8e8f909192939495969798999a9b9c9d9e9fa0a1a2a3a4a5a6a7a8a9aaabacadaeafb0b1b2b3b4b5b6b7b8b9babbbcbdbebfc0c1c2c3c4c5c6c7c8c9cacbcccdcecfd0d1d2d3d4d5d6d7d8d9dadbdcdddedfe0e1e2e3e4e5e6e7e8e9eaebecedeeeff0f1f2f3f4f5f6f7f8f9fafbfcfdfeff", "1cWB5HCBdLjAuqGGReWE3R3CguuwSjw6RHn39s2yuDRTS5NsBgNiFpWgAnEx6VQi8csexkgYw3mdYrMHr8x9i7aEwP8kZ7vccXWqKDvGv3u1GxFKPuAkn8JCPPGDMf3vMMnbzm6Nh9zh1gcNsMvH3ZNLmP5fSG6DGbbi2tuwMWPthr4boWwCxf7ewSgNQeacyozhKDDQQ1qL5fQFUW52QKUZDZ5fw3KXNQJMcNTcaB723LchjeKun7MuGW5qyCBZYzA1KjofN1gYBV3NqyhQJ3Ns746GNuf9N2pQPmHz4xpnSrrfCvy6TVVz5d4PdrjeshsWQwpZsZGzvbdAdN8MKV5QsBDY"},
+
+                // Extra tests
+
+                {"00", "1"},
+                {"00010203040506070809", "1kA3B2yGe2z4"},
+            };
+
+            foreach (var entry in bitcoinTest)
+            {
+                Base58.Encode(entry.Key.HexToBytes()).Should().Be(entry.Value);
+                Base58.Decode(entry.Value).Should().BeEquivalentTo(entry.Key.HexToBytes());
+
+                Action action = () => Base58.Decode(entry.Value + "l");
+                action.Should().Throw<FormatException>();
+            }
         }
     }
 }

neo/Cryptography/Base58.cs

@@ -11,45 +11,46 @@ public static class Base58
 
         public static byte[] Decode(string input)
         {
-            BigInteger bi = BigInteger.Zero;
-            for (int i = input.Length - 1; i >= 0; i--)
+            // Decode Base58 string to BigInteger 
+            var bi = BigInteger.Zero;
+            for (int i = 0; i < input.Length; i++)
             {
-                int index = Alphabet.IndexOf(input[i]);
-                if (index == -1)
-                    throw new FormatException();
-                bi += index * BigInteger.Pow(58, input.Length - 1 - i);
+                int digit = Alphabet.IndexOf(input[i]);
+                if (digit < 0)
+                    throw new FormatException(string.Format("Invalid Base58 character `{0}` at position {1}", input[i], i));
+                bi = bi * 58 + digit;
             }
-            byte[] bytes = bi.ToByteArray();
-            Array.Reverse(bytes);
-            bool stripSignByte = bytes.Length > 1 && bytes[0] == 0 && bytes[1] >= 0x80;
-            int leadingZeros = 0;
-            for (int i = 0; i < input.Length && input[i] == Alphabet[0]; i++)
-            {
-                leadingZeros++;
-            }
-            byte[] tmp = new byte[bytes.Length - (stripSignByte ? 1 : 0) + leadingZeros];
-            Array.Copy(bytes, stripSignByte ? 1 : 0, tmp, leadingZeros, tmp.Length - leadingZeros);
-            Array.Clear(bytes, 0, bytes.Length);
-            return tmp;
+
+            // Encode BigInteger to byte[]
+            // Leading zero bytes get encoded as leading `1` characters
+            int leadingZeroCount = input.TakeWhile(c => c == '1').Count();
+            var leadingZeros = new byte[leadingZeroCount];
+            var bytesWithoutLeadingZeros =
+                bi.ToByteArray()
+                .Reverse()// to big endian
+                .SkipWhile(b => b == 0);//strip sign byte
+            return leadingZeros.Concat(bytesWithoutLeadingZeros).ToArray();
         }
 
         public static string Encode(byte[] input)
         {
+            // Decode byte[] to BigInteger
             BigInteger value = new BigInteger(new byte[1].Concat(input).Reverse().ToArray());
-            StringBuilder sb = new StringBuilder();
-            while (value >= 58)
+
+            // Encode BigInteger to Base58 string
+            var sb = new StringBuilder();
+
+            while (value > 0)
             {
-                BigInteger mod = value % 58;
-                sb.Insert(0, Alphabet[(int)mod]);
+                int remainder = (int)(value % 58);
                 value /= 58;
+                sb.Insert(0, Alphabet[remainder]);
             }
-            sb.Insert(0, Alphabet[(int)value]);
-            foreach (byte b in input)
+
+            // Append `1` for each leading 0 byte
+            for (int i = 0; i < input.Length && input[i] == 0; i++)
             {
-                if (b == 0)
-                    sb.Insert(0, Alphabet[0]);
-                else
-                    break;
+                sb.Insert(0, "1");
             }
             return sb.ToString();
         }