org.bitcoinj.core

Class Base58

java.lang.Object

org.bitcoinj.core.Base58

public class Base58
extends Object

Base58 is a way to encode Bitcoin addresses (or arbitrary data) as alphanumeric strings.

Note that this is not the same base58 as used by Flickr, which you may find referenced around the Internet.

You may want to consider working with VersionedChecksummedBytes instead, which adds support for testing the prefix and suffix bytes commonly found in addresses.

Satoshi explains: why base-58 instead of standard base-64 encoding?

• Don't want 0OIl characters that look the same in some fonts and could be used to create visually identical looking account numbers.
• A string with non-alphanumeric characters is not as easily accepted as an account number.
• E-mail usually won't line-break if there's no punctuation to break at.
• Doubleclicking selects the whole number as one word if it's all alphanumeric.

However, note that the encoding/decoding runs in O(n²) time, so it is not useful for large data.

The basic idea of the encoding is to treat the data bytes as a large number represented using base-256 digits, convert the number to be represented using base-58 digits, preserve the exact number of leading zeros (which are otherwise lost during the mathematical operations on the numbers), and finally represent the resulting base-58 digits as alphanumeric ASCII characters.

Field Summary

Fields

Modifier and Type	Field and Description
static char[]	ALPHABET

Constructor Summary

Constructors

Constructor and Description
Base58()

Method Summary

Modifier and Type	Method and Description
static byte[]	decode(String input) Decodes the given base58 string into the original data bytes.
static byte[]	decodeChecked(String input) Decodes the given base58 string into the original data bytes, using the checksum in the last 4 bytes of the decoded data to verify that the rest are correct.
static BigInteger	decodeToBigInteger(String input)
static String	encode(byte[] input) Encodes the given bytes as a base58 string (no checksum is appended).

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

ALPHABET

public static final char[] ALPHABET

Constructor Detail

Base58

public Base58()

Method Detail

encode

public static String encode(byte[] input)

Encodes the given bytes as a base58 string (no checksum is appended).

Parameters:

input - the bytes to encode

Returns:

the base58-encoded string

decode

public static byte[] decode(String input)
                     throws AddressFormatException

Decodes the given base58 string into the original data bytes.

Parameters:

input - the base58-encoded string to decode

Returns:

the decoded data bytes

Throws:

AddressFormatException - if the given string is not a valid base58 string

decodeToBigInteger

public static BigInteger decodeToBigInteger(String input)
                                     throws AddressFormatException

Throws:

AddressFormatException

decodeChecked

public static byte[] decodeChecked(String input)
                            throws AddressFormatException

Decodes the given base58 string into the original data bytes, using the checksum in the last 4 bytes of the decoded data to verify that the rest are correct. The checksum is removed from the returned data.

Parameters:

input - the base58-encoded string to decode (which should include the checksum)

Throws:

AddressFormatException - if the input is not base 58 or the checksum does not validate.