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20S Networks CS 4457 - Shared screen with speaker view
Seth Dolin
14:46
Yeah we can hear you
Alex Kim
14:47
I can hear you
Seth Dolin
14:54
Yep
Catherine Rogers
14:55
all good
Alex Kim
14:55
I can see the slides as well
Jake Moses
28:50
Nonce is the same for both encrypthing and decrypting right?
Nathan Hunter
29:24
Yeah
Jake Moses
29:30
Thx
Seth Dolin
30:05
Why is the nonce necessary if the cipher is not reversible without the secret key?
Jake Moses
30:51
In case someone intercepts the message and tries to figure out the key themself
Jake Moses
31:05
This way the key is slightly different each time in case it is no longer secure
Andy Tan
31:26
The nonce introduces randomness into the message, so that if you send the same message, you still get a different ciphertext
Grady Roberts
33:14
xor again to decrypt
Alex Kim
33:16
We can decrypt it by XORing it with the key
Josh Laney
39:37
could you make this multi-use by adding a nonce to the key?
Sonia
40:47
you could xor them?
Seth Dolin
42:21
If you were encrypting something that does have entropy like say a bank account number, would this attack still work if you had enough ciphertexts?
Nathan Hunter
50:17
Is this the same problem as using a one-time pad multiple times?
Ryan Heilman
50:58
c1 = c2
Seth Dolin
50:59
They would also be the same
Sonia
54:51
a nonce?
Nathan Hunter
55:37
What's the range of IVs given a 128-bit key?
Jake Moses
01:01:13
If anyone can compute a tag then anyone can mimic that tag
Seth Dolin
01:01:18
Then you can modify the message and insert the hash for the modified message
Josh Laney
01:01:37
to clarify, bob and alice has two keys one for the message and one for the tag?
Jake Moses
01:03:59
Is S for secret?
Nathan Hunter
01:08:35
Define authenticity
Seth Dolin
01:08:36
So for that to work you would encrypt the payload and then compute the mac on the concatenation of the packet headers and the encrypted part of the payload?
Kwadwo Tenkorang
01:11:54
how is the shared key initially shared securely?
Seth Dolin
01:13:56
Alice encrypts the shared key with bobs public key
Grady Roberts
01:33:57
Thank you!
Jessica Krynitsky
01:34:04
Thank you!
Jack Schefer
01:34:04
thank you!
Ryan Heilman
01:34:05
Interesting lecture. Thank you!
Sonia
01:34:10
Thanks so much!