encrypted, or hashed? [LWN.net]

encrypted, or hashed?

Posted Apr 14, 2008 19:38 UTC (Mon) by astrophoenix (guest, #13528)
Parent article: Improving syncookies

forgive me if I sound ignorant, but this sentence doesn't make sense to 
me:

"This encoded information is cryptographically hashed with a secret key 
to form the sequence number of the SYN-ACK and sent to the client."

Shouldn't it read something like "encrypted with a secret key", rather 
than "cryptographically hashed with a secret key"? I was thinking if it 
was hashed, the kernel wouldn't be able to decode it when the ack comes 
in.

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encrypted, or hashed?

Posted Jul 14, 2008 7:39 UTC (Mon) by hso (guest, #24163) [Link]

> Shouldn't it read something like "encrypted with a secret key", rather 
> than "cryptographically hashed with a secret key"? I was thinking if it 
> was hashed, the kernel wouldn't be able to decode it when the ack comes 
> in.

No. It's using a hash algorithm with a key. Saying "encrypted with a secret key" would be
incorrect. Hash algorithms definitely != cipher algorithms.