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Java implementation
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@SamouraiDev
SamouraiDev committed Jul 23, 2017
1 parent 20c2746 commit 105cca3
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27 changes: 27 additions & 0 deletions 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)
97 changes: 97 additions & 0 deletions 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>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>3.0</version>
</dependency>
<dependency>
<groupId>commons-codec</groupId>
<artifactId>commons-codec</artifactId>
<version>1.9</version>
</dependency>
</dependencies>

</project>
154 changes: 154 additions & 0 deletions ref/java/src/main/java/org/bech32/Bech32.java
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package org.bech32;

import org.apache.commons.lang3.tuple.Pair;

public class Bech32 {

private static final String CHARSET = "qpzry9x8gf2tvdw0s3jn54khce6mua7l";

public static String bech32Encode(byte[] hrp, byte[] data) {

byte[] chk = createChecksum(hrp, 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.length + xlat.length + 1];
System.arraycopy(hrp, 0, ret, 0, hrp.length);
System.arraycopy(new byte[] { 0x31 }, 0, ret, hrp.length, 1);
System.arraycopy(xlat, 0, ret, hrp.length + 1, xlat.length);

return new String(ret);
}

public static Pair<byte[], byte[]> bech32Decode(String bech) throws Exception {

if(!bech.equals(bech.toLowerCase()) && !bech.equals(bech.toUpperCase())) {
throw new Exception("bech32 cannot mix upper and lower case");
}

byte[] buffer = bech.getBytes();
for(byte b : buffer) {
if(b < 0x21 || b > 0x7e) {
throw new Exception("bech32 characters out of range");
}
}

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(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) {

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;
}

}
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