Bitcoin/address validation: Difference between revisions
New post showing an alternative version of an existing example which was retained.
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(New post showing an alternative version of an existing example which was retained.) |
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}
}</syntaxhighlight>
===Alternative Version===
This example uses the Java code from the SHA-256 task as an alternative to using Java's built-in SHA256 method. It
also decodes Base58 without using Java's built-in BigInteger class.
<syntaxhighlight lang="java">
import java.nio.charset.StandardCharsets;
import java.util.Arrays;
import java.util.List;
public final class BitcoinAddressValidation {
public static void main(String[] args) {
List<String> addresses = List.of ( "1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i",
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62j",
"1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nK9",
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62X",
"1ANNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i" );
for ( String address : addresses ) {
System.out.println(address + " : " + isValid(address));
}
}
private static boolean isValid(String address) {
if ( address.length() < 26 || address.length() > 35 ) {
throw new AssertionError("Invalid length of bitcoin address");
}
byte[] decoded = decodeBase58(address);
byte[] first21 = Arrays.copyOfRange(decoded, 0, 21);
// Convert 'first21' into an ASCII string for the first SHA256 hash
String text = new String(first21, StandardCharsets.ISO_8859_1);
String hashOne = SHA256.messageDigest(text);
// Convert 'hashOne' into an ASCII string for the second SHA256 hash
byte[] bytesOne = hexToBytes(hashOne);
String asciiOne = new String(bytesOne, StandardCharsets.ISO_8859_1);
String hashTwo = SHA256.messageDigest(asciiOne);
byte[] bytesTwo = hexToBytes(hashTwo);
byte[] checksum = Arrays.copyOfRange(bytesTwo, 0, 4);
byte[] last4 = Arrays.copyOfRange(decoded, 21, 25);
return Arrays.equals(last4, checksum);
}
private static byte[] decodeBase58(String text) {
byte[] result = new byte[25];
for ( char ch : text.toCharArray() ) {
int index = ALPHABET.indexOf(ch);
if ( index == -1 ) {
throw new AssertionError("Invalid character found in bitcoin address: " + ch);
}
for ( int i = result.length - 1; i > 0; i-- ) {
index += 58 * (int) ( result[i] & 0xFF );
result[i] = (byte) ( index & 0xFF );
index >>= 8;
}
if ( index != 0 ) {
throw new AssertionError("Bitcoin address is too long");
}
}
return result;
}
private static byte[] hexToBytes(String text) {
byte[] bytes = new byte[text.length() / 2];
for ( int i = 0; i < text.length(); i += 2 ) {
final int firstDigit = Character.digit(text.charAt(i), 16);
final int secondDigit = Character.digit(text.charAt(i + 1), 16);
bytes[i / 2] = (byte) ( ( firstDigit << 4 ) + secondDigit );
}
return bytes;
}
private static final String ALPHABET = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
}
</syntaxhighlight>
{{ out }}
<pre>
1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i : true
1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62j : false
1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nK9 : true
1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62X : false
1ANNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i : false
</pre>
=={{header|Julia}}==
{{works with|Julia|0.6}}
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