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.




  • 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: