From 769dcf3c008c3686e2348ddabade65766d25d286 Mon Sep 17 00:00:00 2001
From: AB <andre@syntifi.com>
Date: Fri, 16 Sep 2022 15:12:22 +0200
Subject: [PATCH] Adding MixedCaseChecksum feature implementing CEP57 standard

---
 .../key/checksum/MixedCaseChecksum.java       | 58 +++++++++++++------
 .../syntifi/crypto/key/hash/Keccak256.java    | 13 +++++
 .../key/checksum/MixedCaseChecksumTest.java   | 30 +++++++---
 .../syntifi/crypto/key/hash/Blake2bTest.java  | 16 +++++
 .../crypto/key/hash/Keccak256Test.java        | 14 +++++
 5 files changed, 104 insertions(+), 27 deletions(-)
 create mode 100644 crypto-key-common/src/main/java/com/syntifi/crypto/key/hash/Keccak256.java
 create mode 100644 crypto-key-common/src/test/java/com/syntifi/crypto/key/hash/Blake2bTest.java
 create mode 100644 crypto-key-common/src/test/java/com/syntifi/crypto/key/hash/Keccak256Test.java

diff --git a/crypto-key-common/src/main/java/com/syntifi/crypto/key/checksum/MixedCaseChecksum.java b/crypto-key-common/src/main/java/com/syntifi/crypto/key/checksum/MixedCaseChecksum.java
index 1500b84..2097ec7 100644
--- a/crypto-key-common/src/main/java/com/syntifi/crypto/key/checksum/MixedCaseChecksum.java
+++ b/crypto-key-common/src/main/java/com/syntifi/crypto/key/checksum/MixedCaseChecksum.java
@@ -1,11 +1,11 @@
 package com.syntifi.crypto.key.checksum;
 
-import org.bouncycastle.jcajce.provider.digest.Keccak;
-import org.bouncycastle.util.encoders.Hex;
+import com.syntifi.crypto.key.encdec.Hex;
+import com.syntifi.crypto.key.hash.Blake2b;
+import com.syntifi.crypto.key.hash.Keccak256;
 
 /**
- * Implementation of the EIP-55: Mixed-case checksum address encoding
- * Documentation available at: https://eips.ethereum.org/EIPS/eip-55
+ * Mixed checksumEncoding
  *
  * @author Alexandre Carvalho
  * @author Andre Bertolace
@@ -13,26 +13,48 @@
  */
 public class MixedCaseChecksum {
 
-    public static String kekkac256(String value) {
-        Keccak.DigestKeccak kekkac256 = new Keccak.Digest256();
-        byte[] hash = kekkac256.digest(value.getBytes());
-        return Hex.toHexString(hash);
-    }
-
-    public static String checksumEncode(String address) {
-        Boolean withPrefix = address.startsWith("0x");
-        String value = address.toLowerCase().replace("0x", "");
-        char[] hash = kekkac256(value).toCharArray();
+    /**
+     * Implementation of the EIP-55: Mixed-case checksum address encoding
+     * Documentation available at: https://eips.ethereum.org/EIPS/eip-55
+     *
+     * @param value Hex string
+     * @return
+     */
+    public static String checksumEncodeEIP55(String value) {
+        char[] hash = Hex.encode(Keccak256.digest(value.toLowerCase().getBytes())).toCharArray();
         char[] chars = value.toCharArray();
         char[] encoded = new char[chars.length];
         for (int i = 0; i < chars.length; i++) {
             encoded[i] = Character.digit(hash[i], 16) > 7
                     ? Character.toUpperCase(chars[i])
-                    : chars[i];
+                    : Character.toLowerCase(chars[i]);
         }
-        return withPrefix
-                ? "0x" + String.valueOf(encoded)
-                : String.valueOf(encoded);
+        return String.valueOf(encoded);
     }
 
+    /**
+     * Implementation of the CEP-57
+     * Documentation available at: https://github.com/casper-network/ceps/blob/master/text/0057-checksummed-addresses.md
+     *
+     * @param value Hex string
+     * @return
+     */
+    public static String checksumEncodeCEP57(String value) {
+        byte[] hash = Blake2b.digest(Hex.decode(value), 32);
+        char[] chars = value.toCharArray();
+        char[] encoded = new char[chars.length];
+        int whichByte = 0;
+        int whichBit = 0;
+        for (int i = 0; i < chars.length; i++) {
+            boolean bitSet = (Byte.toUnsignedInt(hash[whichByte]) & (1<<whichBit)) != 0;
+            if (Character.isAlphabetic(chars[i])) {
+                encoded[i] = bitSet ? Character.toUpperCase(chars[i]) : Character.toLowerCase(chars[i]);
+                whichByte = (whichByte + whichBit/7) % hash.length;
+                whichBit = (whichBit + 1) % 8;
+            } else {
+                encoded[i] = chars[i];
+            }
+        }
+        return String.valueOf(encoded);
+    }
 }
diff --git a/crypto-key-common/src/main/java/com/syntifi/crypto/key/hash/Keccak256.java b/crypto-key-common/src/main/java/com/syntifi/crypto/key/hash/Keccak256.java
new file mode 100644
index 0000000..436e8a6
--- /dev/null
+++ b/crypto-key-common/src/main/java/com/syntifi/crypto/key/hash/Keccak256.java
@@ -0,0 +1,13 @@
+package com.syntifi.crypto.key.hash;
+
+import org.bouncycastle.jcajce.provider.digest.Keccak;
+import org.bouncycastle.util.encoders.Hex;
+
+public class Keccak256 {
+
+    public static byte[] digest(byte[] value) {
+        Keccak.DigestKeccak kekkac256 = new Keccak.Digest256();
+        byte[] hash = kekkac256.digest(value);
+        return hash;
+    }
+}
diff --git a/crypto-key-common/src/test/java/com/syntifi/crypto/key/checksum/MixedCaseChecksumTest.java b/crypto-key-common/src/test/java/com/syntifi/crypto/key/checksum/MixedCaseChecksumTest.java
index c5b7fe8..52b9bc1 100644
--- a/crypto-key-common/src/test/java/com/syntifi/crypto/key/checksum/MixedCaseChecksumTest.java
+++ b/crypto-key-common/src/test/java/com/syntifi/crypto/key/checksum/MixedCaseChecksumTest.java
@@ -6,20 +6,32 @@
 public class MixedCaseChecksumTest {
 
     @Test
-    void shouldMatchLowerCaseAddress() {
-        assertEquals("0xfB6916095ca1df60bB79Ce92cE3Ea74c37c5d359",
-                MixedCaseChecksum.checksumEncode("0xfb6916095ca1df60bb79ce92ce3ea74c37c5d359"));
+    void eip55ShouldMatchLowerCaseAddress() {
+        assertEquals("fB6916095ca1df60bB79Ce92cE3Ea74c37c5d359",
+                MixedCaseChecksum.checksumEncodeEIP55("fb6916095ca1df60bb79ce92ce3ea74c37c5d359"));
     }
 
     @Test
-    void shouldMatchUpperCaseAddress() {
-        assertEquals("0xfB6916095ca1df60bB79Ce92cE3Ea74c37c5d359",
-                MixedCaseChecksum.checksumEncode("0xFB6916095CA1DF60BB79CE92CE3EA74C37C5D359"));
+    void eip55ShouldMatchUpperCaseAddress() {
+        assertEquals("fB6916095ca1df60bB79Ce92cE3Ea74c37c5d359",
+                MixedCaseChecksum.checksumEncodeEIP55("FB6916095CA1DF60BB79CE92CE3EA74C37C5D359"));
     }
 
     @Test
-    void kekkac256ShouldMatch() {
-        assertEquals("a9059cbb2ab09eb219583f4a59a5d0623ade346d962bcd4e46b11da047c9049b",
-                MixedCaseChecksum.kekkac256("transfer(address,uint256)"));
+    void cep57houldMatchEmptyAddress() {
+        assertEquals("",
+                MixedCaseChecksum.checksumEncodeEIP55(""));
     }
+    @Test
+    void cep57houldMatchLowerCaseAddress() {
+        assertEquals("010573D52dFA032716fDC2AE5396987f280304106fC11f6Ac6Ccf287B81dc09ED7",
+                MixedCaseChecksum.checksumEncodeCEP57("010573d52dfa032716fdc2ae5396987f280304106fc11f6ac6ccf287b81dc09ed7"));
+    }
+
+    @Test
+    void cep57houldMatchUpperCaseAddress() {
+        assertEquals("51DA5aE5C39880Bfe4f94B0898332d1BD37e647F72f79Cf23475df1Bb1f85bEA",
+                MixedCaseChecksum.checksumEncodeCEP57("51da5ae5c39880bfe4f94b0898332d1bd37e647f72f79cf23475df1bb1f85bea"));
+    }
+
 }
diff --git a/crypto-key-common/src/test/java/com/syntifi/crypto/key/hash/Blake2bTest.java b/crypto-key-common/src/test/java/com/syntifi/crypto/key/hash/Blake2bTest.java
new file mode 100644
index 0000000..041c4e9
--- /dev/null
+++ b/crypto-key-common/src/test/java/com/syntifi/crypto/key/hash/Blake2bTest.java
@@ -0,0 +1,16 @@
+package com.syntifi.crypto.key.hash;
+
+import com.syntifi.crypto.key.encdec.Hex;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+import java.nio.charset.StandardCharsets;
+
+public class Blake2bTest {
+
+    @Test
+    void test() {
+        Assertions.assertEquals("44682ea86b704fb3c65cd16f84a76b621e04bbdb3746280f25cf062220e471b4",
+                Hex.encode(Blake2b.digest("أبو يوسف يعقوب بن إسحاق الصبّاح الكندي‎".getBytes(StandardCharsets.UTF_8), 32)));
+    }
+}
diff --git a/crypto-key-common/src/test/java/com/syntifi/crypto/key/hash/Keccak256Test.java b/crypto-key-common/src/test/java/com/syntifi/crypto/key/hash/Keccak256Test.java
new file mode 100644
index 0000000..114637b
--- /dev/null
+++ b/crypto-key-common/src/test/java/com/syntifi/crypto/key/hash/Keccak256Test.java
@@ -0,0 +1,14 @@
+package com.syntifi.crypto.key.hash;
+
+import com.syntifi.crypto.key.encdec.Hex;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class Keccak256Test {
+
+    @Test
+    void kekkac256ShouldMatch() {
+        Assertions.assertEquals("a9059cbb2ab09eb219583f4a59a5d0623ade346d962bcd4e46b11da047c9049b",
+                Hex.encode(Keccak256.digest("transfer(address,uint256)".getBytes())));
+    }
+}