Vanitygen has the option for a file to contain random numbers as an alternative to the built-in random number generator.

What is the correct way to generate this file on Windows, OSX? (and Linux)

What is the range of each number (upper and lower bound)?

What is the correct format of the file (CRLF, LF only)?

3 Answers 3


It uses RAND_load_file function from OpenSSL, which accepts any binary input - random bytes. Under Linux and OSX the /dev/random file can be used, I don't know equivalent under Windows. However, OpenSSL uses /dev/random by default, so there is no improvement using it explicitly.

Only scenario might be when you need faster random numbers generator, as /dev/random is quite slow and you start vanitygen very often. Then you can for example use /dev/urandom (but in this case you expose yourself to small but perhaps exploitable possibility that the seeds for generated addresses will be related). Certified hardware random numbers generators would be preferred in this case (some recent Intel and VIA CPUs have one).


Do not use such a file from any (public) source!

Generate it yourself always, preferable off-line.

On linux:

dd if=/dev/urandom bs=1024 count=1 2> /dev/null 1> seed.bin

This file can be read by vanitygen if you execute it with the -s option, like so:

$ ./vanitygen64 -v -s ./seed.bin 1XYZ1
Read 1024 bytes from RNG seed file
Prefix difficulty:            264104224 1XYZ1


or you can get some random bytes file ftom http://www.random.org/ and use it as your imput

  • 1
    Actually it is not recommended since data from random.org is public and it could be used to attack you.
    – Felipe
    Commented Nov 27, 2015 at 6:00

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.