All Questions
Tagged with cbc-mac authentication
9 questions
1
vote
1
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165
views
Why CBC-MAC encrypts at each step
Considering CBC-MAC as:
$\qquad H_0 = IV = 0$
$\qquad H_i = E_k(P_i \oplus H_{i-1})$
$\qquad MAC = H_n$
What are the properties that makes this "safer" (less ...
- 129
1
vote
1
answer
98
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CCM authenticity bound
Can someone help me understanding the CCM authenticity bound by Phillip Rogaway?
i-e Success probability < $q_{\text{dec}}/2^\tau + \sigma/2^b$.
$\tau$ is tag length, where as $b$ is block length. ...
- 37
0
votes
1
answer
349
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CBC-MAC 8 octet ICV compatable with 16 octet block size?
I'm trying to use DTLS in Preshared key mode for CoAP which necessitates using CipherSuite TLS_PSK_WITH_AES_128_CCM_8
I'm trying to start with the CBC-MAC but I'm not sure how to get an 8 octet ICV ...
- 103
0
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1
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562
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Enc-Mac (AES CTR+CBC) mixing AES-256 and AES-128 and splitting keys
I'm looking to accomplish a Enc-then-Mac approach using
AES-CTR
and
ECBC-MAC
Now ECBC-MAC requires 2 distinct keys, one for the MAC, and one to encrypt the Tag.
If I do this:
Use AES256-CTR for the ...
- 1
5
votes
1
answer
12k
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Insecurity of CBC-MAC
Can anyone explain why CBC-MAC is not secure for variable length message?
I read many books, but there are still some confusion. Such as the highlighted parts in previous pictures
Questions:
why ...
- 133
3
votes
1
answer
3k
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Why is CBC-MAC with length appended not secure?
I've just read about CBC-MAC for the authentication of arbitrary length messages. In particular I cannot figure out why appending the message length before computing the MAC yields a non-secure MAC. I'...
- 81
1
vote
1
answer
611
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Few questions about CBC MAC
I want to use CBC MAC. First I hope to find some implementation of block cipher which I will use in CBC mode, which I understand is CBC MAC. But I have two questions:
1) If the length of the message ...
user29112
1
vote
1
answer
2k
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MAC tag size in AES CCM, when using CTR + CBC-MAC (not CBC MAC only)
Assuming that AES CCM is used with respect of the NONCE unicity // the key life cycle, I wonder about the need of using the highest size for CBC-MAC authentication tag if CTR mode encrypts both ...
- 105
2
votes
1
answer
2k
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CBC-MAC: is it secure to authenticate a fixed length ciphertext?
Suppose I have a fixed-length arbitrary ciphertext.
To authenticate such ciphertext:
I generate a random AES Key $K_{auth}$.
Then I compute the CBC-MAC Tag of the ciphertext with $K_{auth}$.
Finally,...
- 23