[Cryptography] Feedback welcome on autentication/password replacement idea

[Howard Chu]

Howard Chu wrote:
> Ilya Kasnacheev wrote:
>> Hello, I want to share my idea with you. If some places are not clear enough,
>> you can try to guess or just ask me.
>>
>> Main idea:
>> Boris hashes some secret value many many times recursively (SHA(X),
>> SHA(SHA(X)), ...), yielding chain of hashes.
>> Boris gives the last hash in chain to Anne. When Boris want to prove that he
>> came back and is genuine, he transmits previous hash in the chain. Anne hashes
>> it and looks up if she saw that hash before - if she did, it's really Boris.
>>
>> Are there holes in this scheme?
>
> This is precisely how S/Key works.

Funny to see this pop up now, it's been over 20 years since I worked on that code.

https://github.com/dkorunic/pam_skey/blob/master/libskey/README#L383-L400

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   -- Howard Chu
   CTO, Symas Corp.           http://www.symas.com
   Director, Highland Sun     http://highlandsun.com/hyc/
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