Client and backend. This class is shared: the same code is compiled into your app and into your server, so everything on this page works in both.

public final class Mnemonic

Object
Mnemonic

BIP-39 mnemonic sentences: the 12 to 24 English words a wallet shows as its backup, and the 64-byte seed Bip32 and Slip10 derive every key from.

String words = Mnemonic.generate(128);           // 12 words
byte[] seed = Mnemonic.toSeed(words, "");        // the empty passphrase
Bip32 account = Bip32.master(seed).derive("m/44'/60'/0'/0/0");

Only the English wordlist is built in, which is what every wallet exports by default.

Methods

`public static` `String generate(int strengthBits)`	A new mnemonic over fresh entropy from the platform CSPRNG.
`public static` `String fromEntropy(byte[] entropy)`	The mnemonic that encodes `entropy` (16 to 32 bytes, a multiple of 4).
`public static byte[] toEntropy(String mnemonic)`	The entropy a mnemonic encodes, after checking every word and the checksum.
`public static boolean isValid(String mnemonic)`	Tells whether the text is a mnemonic with known words and a correct checksum.
`public static byte[] toSeed(String mnemonic, String passphrase)`	The 64-byte BIP-39 seed: PBKDF2-HMAC-SHA512 over the words, salted with `"mnemonic" + passphrase`, 2048 iterations.
`public static int indexOf(String word)`	The position of an English word in the BIP-39 list, or -1.
`public static` `String word(int index)`	The English word at `index` (0 to 2047).

Inherited methods

From Object

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

Method details

generate

public static String generate(int strengthBits)

A new mnemonic over fresh entropy from the platform CSPRNG.

Parameters

strengthBits int: 128, 160, 192, 224 or 256, for 12, 15, 18, 21 or 24 words

fromEntropy

public static String fromEntropy(byte[] entropy)

The mnemonic that encodes entropy (16 to 32 bytes, a multiple of 4).

toEntropy

public static byte[] toEntropy(String mnemonic)

The entropy a mnemonic encodes, after checking every word and the checksum.

Throws

IllegalArgumentException: for an unknown word, a word count other than 12, 15, 18, 21 or 24, or a checksum mismatch

isValid

public static boolean isValid(String mnemonic)

Tells whether the text is a mnemonic with known words and a correct checksum.

toSeed

public static byte[] toSeed(String mnemonic, String passphrase)

The 64-byte BIP-39 seed: PBKDF2-HMAC-SHA512 over the words, salted with "mnemonic" + passphrase, 2048 iterations. The words are not checked, as the specification asks; call isValid first to reject a mistyped backup.

BIP-39 normalizes both strings to Unicode NFKD before encoding them as UTF-8. The words always are ASCII and the device class library has no normalizer, so a passphrase outside ASCII must be given already in NFKD form – a precomposed accent otherwise derives a different wallet than other software does.

Parameters

mnemonic String: the words, separated by whitespace
passphrase String: the optional extra word (“25th word”); null or "" for none

indexOf

public static int indexOf(String word)

The position of an English word in the BIP-39 list, or -1.

word

public static String word(int index)

The English word at index (0 to 2047).