RPASS(1) General Commands Manual RPASS(1)

rpass — strong password generator for humans

rpass [-V] [bitlen]

rpass is a strong password generator for human beings. The generated passwords are shorter than Diceware which suits them better for use on mobile devices, the command line or other environments where one has to frequently type the password. The passwords are case-insensitive so that there is no alternation between keyboards on insert. Blanks can be inserted at arbitrary places to enhance visual representation. Furthermore, the passwords are both visually and phonetically unambiguous.

Print the version of rpass.
bitlen
Use a key space of the specified bit length, defaults to 40.

In order to determine the right bitlen three factors should be considered:

  1. the hashing mechanism used to store the password
  2. the time for which this password has to be secure
  3. the processing power of the adversary

The default bitlen of 40 bits relies on the following requirements: the password is stored using bcrypt(3) with 2^10 rounds, it should only be secure for one year and the adversary has no more than $25,000.00 to spend on brute forcing the password (as of 2019).

The rpass utility exits 0 on success, and >0 if an error occurs.

Random password from the default key space:

$ rpass
jikmus xuzjex

Random password from an 80 bit key space:

$ rpass 80
jultar ramlap rinwun bemvuh

In order to calculate the required bitlen let's consider a scenario with the following requirements: the generated password will be used for at most half a year and is stored using PBKDF2-HMAC-SHA256 with a million iterations. Furthermore the adversary has $25,000.00 to spend. According to “8x Nvidia GTX 1080 Ti Hashcat Benchmarks” as of 2019 the adversary can try 15 million hashes per second on PBKDF2-HMAC-SHA256 with a thousand iterations. This would be 15 thousand hashes per second on PBKDF2-HMAC-SHA256 with a million iterations. Hence the required key space is 15,000 * 3,600 * 24 * 183 * 2 = 38.8 bits.

bcrypt(3), 8x Nvidia GTX 1080 Ti Hashcat Benchmarks The Diceware Passphrase Home Page PKCS #5: Password-Based Cryptography Specification

Tim Kuijsten

The phonetic ambiguity of the current set of mnemonics depends on the spoken language and is currently optimized for the Dutch language.

December 13, 2019 OpenBSD 6.6