SLIP39

Modified on Thu, 24 Dec, 2020 at 1:16 PM

SLIP39 STANDARD

SLIP39: Satoshi Labs Improvement Proposal 39

SLIP39 is an open-source cryptography standard proposed in 2013 by Pavol Rusnak, Andrew Kozlik, Ondrej Vejpustek, Tomas Susanka, Marek Palatinus and Jochen Hoenicke.

SLIP39 implements Shamir Secret Sharing (SSS) for a master seed. It splits the secret in different shares and defines a minimum number of shares required to reveal it. This number is call the threshold.

Every shares are composed of 20 or 33 words. They are meant to be distributed amongst different participants or separate locations.

Every shares are a different list of words in a specific order and each word can be uniquely identified by its four first letters. SLIP39 words are pulled from a specific wordlist that will never change:
- https://github.com/satoshilabs/slips/blob/master/slip-0039/wordlist.txt

SLIP39 ENCRYPTION

To create a SLIP39 share, the initial entropy value and all the necessary share information to handle Shamir Secret Sharing are split into 10 bits segments and each is then translated into seed words.
Each 10 bits segment represents a decimal number between 0 and 1023 and serves as an index in SLIP39 specific wordlist to convert the initial number into an easily readable form. That is why this list is made of 1024 words.

Each share is independent from the other. It means that the shares don’t leak any information about the other shares.

Initial entropy + padding + SSS attributes	Share length	Encryption level
128 bits + 2 bits + 70 bits	20 words	128 bits
256 bits + 4 bits + 70 bits	33 words *	256 bits

*Please note that 33 words shares are not supported by HODLR Disks.

More detailed information is available on:
https://github.com/satoshilabs/slips/blob/master/slip-0039.md