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bio website xhalo.tk
location Budapest
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visits member for 6 months
seen May 30 at 15:30

Apr
2
comment Is there a point using GCM block chiper with Authenticated DH?
Yes I know that, if this was in my case, I wouldn't ask the question.
Apr
1
comment Is there a point using GCM block chiper with Authenticated DH?
Yes it is. And since GCM operates with CTR mode that doesn't need unpredictable IV, I'll use GCM with secret IV and counters that also won't let adversary block packets unnoticed. "It's not a bug, it's a feature."
Apr
1
comment Is there a point using GCM block chiper with Authenticated DH?
Ok, so I was thinking on this again, and not sure if I should make a new question for this, but how GCM protects against replay attack? If you send the same untouched packet again and again it will just validate it every time, no?
Mar
31
awarded  Scholar
Mar
31
accepted Is there a point using GCM block chiper with Authenticated DH?
Mar
31
comment Is there a point using GCM block chiper with Authenticated DH?
TCP guaranties that it won't go out of sync, so the worst that can happen that connection terminates, and a reconnection is needed. Anyways, you made it more clear for me, so I accept your answer, thank you. I'll use GCM, since that 16 byte overhead is not a big problem, and has no other drawbacks, and it's also more secure.
Mar
31
comment Is there a point using GCM block chiper with Authenticated DH?
If I remember well, what you said only happens if you use the same one-time pad or IV more than once for a message, whit the same key. Also, for example changing 1 bit in AES-CBC/CTR will produce complete garbage for that block. About replay attacks, it's not a big problem in my case, the important is that the encrypted data should stay secured. Also, if I use a secret IV delivered from the shared secret too with CTR mode, and keep increasing it every packet, it will protect against this attack method.
Mar
31
awarded  Student
Mar
31
asked Is there a point using GCM block chiper with Authenticated DH?
Mar
31
awarded  Informed