Why, what’s the real-world use case of BIP 39?  To ease human memorization, transcription, and communication of pseudorandom strings!

Bitcoin has been a leading innovator in the development of better ways for humans to interact with cryptographic gibberish.  With BIP 39 mnemonics, a mere mortal human can memorize a pseudorandom string, write it into a sealed Last Will and Testament in a manner easy to transcribe back into a computer—or if necessary, whisper it into somebody’s ear...

I should think that people may want to memorize, transcribe, speak, or whisper .onion addresses, too.

As an English speaker, which would you prefer to deal with in your capacity as not being carved out of silicon:  “wlupld3ptjvsgwqw” (ouch!), or “real element glow tennis pluck museum hair shuffle”?  Chinese people may prefer “潔 愛 唱 仰 淚 吳 乎 怒”.

For overlapping reasons, I have also been working on the application of BIP 173 Bech32 encoding for .onion address data (more).  That has the advantage of error correction, and a more compact format; different tools apply to distinct use cases.  Again, Bitcoin technical innovation opens new possibilities in other applications of cryptography.

I am also using these methods with PGP.  I’ve seen PGP mnemonics before, of course—but the mnemonic standard I recollect having seen many years ago used a 256-word (8-bit) alphabet, rather than the 2048-word (11-bit) alphabets from BIP 39.  Thus, unnecessarily long word strings.  I am also working on a spec for what I call Bech32 “PGP Descriptors” to encode key fingerprint plus metadata.  See those ugly hexadecimal strings in my signature?  Bitcoin will provide a better way.

Meanwhile, for use in Bitcoin, I have almost completed full BIP 39 implementation in easyseed(1).  It would have been done yesterday; but for the missing final piece, generation of the output seed, I need means to perform the specified Unicode NFKD normalization without dragging in ugly dependencies.  The rest is trivial.