> On 26 Jan 2017, at 09:59, Arlo Breault <arlo@xxxxxxxxxxxxxx> wrote:
>
>
>> On Jan 24, 2017, at 4:27 AM, George Kadianakis <desnacked@xxxxxxxxxx> wrote:
>>
>> onion_address = base32(pubkey || checksum || version)
>> checksum = SHA3(".onion checksum" || pubkey || version)
>
> Any reason not to have the order of,
> pubkey || checksum || version
> be the same in both?
Yes: ".onion checksum" is not the same as checksum.
>> checksum = SHA3(".onion checksum" || pubkey || version)
Is the standard H(UNIQUE_PREFIX || DATA) construct that resists
hash reuse and rainbow table attacks. ".onion checksum" represents the
bytes from an ASCII-encoded literal string.
Putting those bytes later in the hash opens us up to hash reuse attacks
where the key or version bytes are made to match the prefix from another
hash.
(Every time we do SHA3(... || pubkey || ...) in the hidden service
protocol, we want a prefix that is static and unique, so people can't
use hashes from one part of the protocol to spoof hashes in another part
of the protocol.)
>> onion_address = base32(pubkey || checksum || version)
Is the order in which the address is encoded once the checksum is
calculated. checksum represents (the first two bytes of) the result of
the SHA3 hash.
We put pubkey first so that humans can distinguish addresses.
(We could put checksum first, but that's non-standard.)
T
--
Tim Wilson-Brown (teor)
teor2345 at gmail dot com
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