Java implementation

ref/java/README.md

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+# Bech32
+
+Bech32 implementation in Java.
+
+## Build Process
+
+Install Maven 3.2 or higher.
+
+### Build:
+
+mvn clean
+
+mvn package
+
+Two .jar files will be created in the directory ./target :
+
+Bech32.jar : Can be included in any Java project 'as is' but requires inclusion of dependencies. Main.java harness not included.
+
+Bech32-jar-with-dependencies.jar : includes all dependencies and can be run from the command line using the Main.java harness.
+
+### Run using Main.java harness:
+
+java -jar -ea target/Bech32-jar-with-dependencies.jar
+
+### Dev contact:
+
+[PGP](http://pgp.mit.edu/pks/lookup?op=get&search=0x72B5BACDFEDF39D7)

ref/java/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>org.bech32</groupId>
+    <artifactId>Bech32</artifactId>
+    <packaging>jar</packaging>
+    <version>1.0-SNAPSHOT</version>
+    <name>Bech32</name>
+    <url>http://maven.apache.org</url>
+
+    <properties>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    </properties>
+
+    <build>
+    <finalName>Bech32</finalName>
+
+    <plugins>
+
+        <!-- download source code in Eclipse, best practice -->
+        <plugin>
+            <groupId>org.apache.maven.plugins</groupId>
+            <artifactId>maven-eclipse-plugin</artifactId>
+            <version>2.9</version>
+            <configuration>
+                <downloadSources>true</downloadSources>
+                <downloadJavadocs>false</downloadJavadocs>
+            </configuration>
+        </plugin>
+
+        <!-- Set a compiler level -->
+        <plugin>
+            <groupId>org.apache.maven.plugins</groupId>
+            <artifactId>maven-compiler-plugin</artifactId>
+            <version>2.3.2</version>
+            <configuration>
+                <source>${jdk.version}</source>
+                <target>${jdk.version}</target>
+            </configuration>
+        </plugin>
+
+        <!-- Make this jar executable -->
+        <plugin>
+            <groupId>org.apache.maven.plugins</groupId>
+            <artifactId>maven-jar-plugin</artifactId>
+            <version>2.6</version>
+            <configuration>
+                <excludes>
+                    <exclude>**/Main*</exclude>
+                </excludes>
+            </configuration>
+        </plugin>
+
+        <plugin>
+            <artifactId>maven-assembly-plugin</artifactId>
+            <configuration>
+                <archive>
+                    <manifest>
+                        <mainClass>org.bech32.Main</mainClass>
+                    </manifest>
+                </archive>
+                <descriptorRefs>
+                    <descriptorRef>jar-with-dependencies</descriptorRef>
+                </descriptorRefs>
+            </configuration>
+            <executions>
+                <execution>
+                    <id>make-assembly</id>
+                    <phase>package</phase>
+                    <goals>
+                        <goal>single</goal>
+                    </goals>
+                </execution>
+            </executions>
+        </plugin>
+
+    </plugins>
+
+    </build>
+
+    <dependencies>
+        <dependency>
+            <groupId>commons-codec</groupId>
+            <artifactId>commons-codec</artifactId>
+            <version>1.9</version>
+        </dependency>
+    </dependencies>
+
+</project>

ref/java/src/main/java/org/bech32/Bech32.java

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+package org.bech32;
+
+import java.util.Locale;
+
+public class Bech32 {
+
+    private static final String CHARSET = "qpzry9x8gf2tvdw0s3jn54khce6mua7l";
+
+    public static String bech32Encode(String hrp, byte[] data) {
+
+        byte[] chk = createChecksum(hrp.getBytes(), data);
+        byte[] combined = new byte[chk.length + data.length];
+
+        System.arraycopy(data, 0, combined, 0, data.length);
+        System.arraycopy(chk, 0, combined, data.length, chk.length);
+
+        byte[] xlat = new byte[combined.length];
+        for(int i = 0; i < combined.length; i++)   {
+            xlat[i] = (byte)CHARSET.charAt(combined[i]);
+        }
+
+        byte[] ret = new byte[hrp.getBytes().length + xlat.length + 1];
+        System.arraycopy(hrp.getBytes(), 0, ret, 0, hrp.getBytes().length);
+        System.arraycopy(new byte[] { 0x31 }, 0, ret, hrp.getBytes().length, 1);
+        System.arraycopy(xlat, 0, ret, hrp.getBytes().length + 1, xlat.length);
+
+        return new String(ret);
+    }
+
+    public static Pair<String, byte[]> bech32Decode(String bech) throws Exception  {
+
+        byte[] buffer = bech.getBytes();
+        for(byte b : buffer)   {
+            if(b < 0x21 || b > 0x7e)    {
+                throw new Exception("bech32 characters out of range");
+            }
+        }
+
+        if(!bech.equals(bech.toLowerCase(Locale.ROOT)) && !bech.equals(bech.toUpperCase(Locale.ROOT)))  {
+            throw new Exception("bech32 cannot mix upper and lower case");
+        }
+
+        bech = bech.toLowerCase();
+        int pos = bech.lastIndexOf("1");
+        if(pos < 1)    {
+            throw new Exception("bech32 missing separator");
+        }
+        else if(pos + 7 > bech.length())    {
+            throw new Exception("bech32 separator misplaced");
+        }
+        else if(bech.length() < 8)    {
+            throw new Exception("bech32 input too short");
+        }
+        else if(bech.length() > 90)    {
+            throw new Exception("bech32 input too long");
+        }
+        else    {
+            ;
+        }
+
+        String s = bech.substring(pos + 1);
+        for(int i = 0; i < s.length(); i++) {
+            if(CHARSET.indexOf(s.charAt(i)) == -1)    {
+                throw new Exception("bech32 characters  out of range");
+            }
+        }
+
+        byte[] hrp = bech.substring(0, pos).getBytes();
+
+        byte[] data = new byte[bech.length() - pos - 1];
+        for(int j = 0, i = pos + 1; i < bech.length(); i++, j++) {
+            data[j] = (byte)CHARSET.indexOf(bech.charAt(i));
+        }
+
+        if (!verifyChecksum(hrp, data)) {
+            throw new Exception("invalid bech32 checksum");
+        }
+
+        byte[] ret = new byte[data.length - 6];
+        System.arraycopy(data, 0, ret, 0, data.length - 6);
+
+        return Pair.of(new String(hrp), ret);
+    }
+
+    private static int polymod(byte[] values)  {
+
+        final int[] GENERATORS = { 0x3b6a57b2, 0x26508e6d, 0x1ea119fa, 0x3d4233dd, 0x2a1462b3 };
+
+        int chk = 1;
+
+        for(byte b : values)   {
+            byte top = (byte)(chk >> 0x19);
+            chk = b ^ ((chk & 0x1ffffff) << 5);
+            for(int i = 0; i < 5; i++)   {
+                chk ^= ((top >> i) & 1) == 1 ? GENERATORS[i] : 0;
+            }
+        }
+
+        return chk;
+    }
+
+    private static byte[] hrpExpand(byte[] hrp) {
+
+        byte[] buf1 = new byte[hrp.length];
+        byte[] buf2 = new byte[hrp.length];
+        byte[] mid = new byte[1];
+
+        for (int i = 0; i < hrp.length; i++)   {
+            buf1[i] = (byte)(hrp[i] >> 5);
+        }
+        mid[0] = 0x00;
+        for (int i = 0; i < hrp.length; i++)   {
+            buf2[i] = (byte)(hrp[i] & 0x1f);
+        }
+
+        byte[] ret = new byte[(hrp.length * 2) + 1];
+        System.arraycopy(buf1, 0, ret, 0, buf1.length);
+        System.arraycopy(mid, 0, ret, buf1.length, mid.length);
+        System.arraycopy(buf2, 0, ret, buf1.length + mid.length, buf2.length);
+
+        return ret;
+    }
+
+    private static boolean verifyChecksum(byte[] hrp, byte[] data) {
+
+        byte[] exp = hrpExpand(hrp);
+
+        byte[] values = new byte[exp.length + data.length];
+        System.arraycopy(exp, 0, values, 0, exp.length);
+        System.arraycopy(data, 0, values, exp.length, data.length);
+
+        return (1 == polymod(values));
+    }
+
+    private static byte[] createChecksum(byte[] hrp, byte[] data)  {
+
+        final byte[] zeroes = new byte[] { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
+        byte[] expanded = hrpExpand(hrp);
+        byte[] values = new byte[zeroes.length + expanded.length + data.length];
+
+        System.arraycopy(expanded, 0, values, 0, expanded.length);
+        System.arraycopy(data, 0, values, expanded.length, data.length);
+        System.arraycopy(zeroes, 0, values, expanded.length + data.length, zeroes.length);
+
+        int polymod = polymod(values) ^ 1;
+        byte[] ret = new byte[6];
+        for(int i = 0; i < ret.length; i++)   {
+            ret[i] = (byte)((polymod >> 5 * (5 - i)) & 0x1f);
+        }
+
+        return ret;
+    }
+
+}