[tor-onions] brute forcing Onion domains

[teor]

Hi,

V2 onions are a truncated SHA1. Doing an entire hash is expensive.

V3 onions are an ed25519 key plus a suffix. So if you're just looking
for a prefix, you can choose a random value. Then increment by the
basepoint until you find the prefix you want. (This is a relatively
cheap operation, because you're just adding 255-bit numbers.)

You can save the expensive suffix calculations for the final
candidate keys.

Here's one implementation:
https://github.com/Yawning/horse25519/blob/master/src/horse25519.c#L209  

This is a summary: there are a few important details to get right,
like key masking and security.

T

-- 
teor
----------------------------------------------------------------------


> On 27 Apr 2020, at 06:37, niftybunny <abuse-contact at to-surf-and-protect.net> wrote:
> 
> Hi there,
> 
> quick question. Is there a fundamental time difference between brute forcing V3 to V2 Onion domains or did my 4 lucky feet just stopped working?
> 
> niftybunny
> 
> 
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