# Talk:BIP 0039

From Bitcoin Wiki

Here is a simple implementation of my proposal to 'mine' for a seed:

from electrum import mnemonic import ecdsa import time import hmac import hashlib PREFIX = "100" n = len(PREFIX) entropy = ecdsa.util.randrange( pow(2,160) ) nonce = 0 while True: ss = "%040x"%(entropy+nonce) s = hashlib.sha256(ss.decode('hex')).digest().encode('hex') words = mnemonic.mn_encode(s)[0:13] # 13 random words seed = ' '.join(words) I = hmac.new("Bitcoin mnemonic", seed, hashlib.sha512).digest().encode('hex') if I[0:n] == PREFIX: break nonce += 1 print seed print I

PREFIX contains metadata about the wallet version.

The first 4 or 12 bits of PREFIX encode the length of the metadata (0 to e, f00 to fff)

The length of the metadata in bits is 4*(n+1) where n is the value that is encoded in the first bits.

The format of the metadata itself remains to be defined.

The most compact way to use it is probably to allocate version numbers.

Examples:

- 00 to 0f : length = 4 bits. 16 possible version numbers
- 100 to 1ff : length = 8 bits. 256 possible version numbers. (00 is used for Electrum's wallet structure)
- 2000 to 2fff
- etc.