David Wong

cryptologie.net

cryptography, security, and random thoughts

Hey! I'm David, cofounder of zkSecurity, research advisor at Archetype, and author of the Real-World Cryptography book. I was previously a cryptography architect of Mina at O(1) Labs, the security lead for Libra/Diem at Facebook, and a security engineer at the Cryptography Services of NCC Group. Welcome to my blog about cryptography, security, and other related topics.

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Myths about /dev/urandom

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In one of my class the teacher advise against /dev/urandom.

I wondered why. I remembered reading some articles about random vs urandom and urandom being better, but that was years ago and my memory is not fresh. Wikipedia does advise against it, as does the manpage if you want to generate a long term key.

I also stumbled on one of Thomas Pornin’s answer on the security SO also pointing to a blogpost from Thomas Hühn

tl;dr:

Fact: /dev/urandom is the preferred source of cryptographic randomness on UNIX-like systems.

suggested reads:
→ Generating randomness and you're too close to boot? • blog
→ Why are people so bothered about truly random numbers? • blog
→ Pseudo Random Number Generators using a block cipher in CTR mode • blog
← back to all posts blog • 2014-12-03
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Myths about /dev/urandom
12-03 blog
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