Re: [tor-talk] .onion name gen

[Seth David Schoen <schoen@xxxxxxx>]

Scfith Rise up writes:

> I'm pretty sure that the onion address is generated directly from the private key, at least if you have every played around with scallion or eschalot. So what you just wrote doesn't apply in that way. But again, I could be wrong. 

Mirimir's reference at

https://trac.torproject.org/projects/tor/wiki/doc/HiddenServiceNames

shows that they are truncated SHA-1 hashes, 80 bits in length, of "the
DER-encoded ASN.1 public key" of "an RSA-1024 keypair".

So you have the space of public keys (indeed, it's considerably less than
1024 bits if you want to actually be able to use it as a keypair) and the
space of 80-bit truncated hashes, and the former is dramatically larger
than the latter.  So over the entire space of keys, collisions are not
just possible but are required and even extremely frequent.  On the other
hand, they're so difficult to find that nobody knows a single example!

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Seth Schoen  <schoen@xxxxxxx>
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