# All Questions

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I'm having a hard time understanding why people use constant-time techniques to counter time-attacks, when blinding seems as good and cheaper to implement. Why do people avoid blinding in ECC?
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### DPA Attack on HMAC SHA-256

I have read the paper Differential Power Analysis of HMAC SHA-2 in the Hamming Weight Model and I want to understand the DPA Attack. In section 3.2.1 Path 1 (page 4) there is written: The last ...
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### power consumption in a XOR

I'm trying to understand how a XOR affect traces of power consumption in a Differential Power Analysis on smartcards. What's the difference in energy radiated in a $1 \oplus 1$ and in a $0 \oplus 1$? ...
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### Spritz cipher sponge function capacity

Rivest and Shuldt proposed a new sponge like cipher algorithm called Spritz: http://people.csail.mit.edu/rivest/pubs/RS14.pdf In this paper they say that the strength of the cipher is related to the ...
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### How to calculate the non-linearity of an s-box? [duplicate]

I am struggling to understand how to calculate non-linearty of an s-box, could someone show me a detailed example? I found “How to calculate non linearity of AES S-box?” which helped a little, but I ...
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### Concerns about use of MAC in my specification

Here is the pseudocode for a routine I am designing: ...
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### Relationship between an elements order and the DLP [closed]

How can I use these properties to attack the DHKE? I know that the order of $a$ is always $2$ for $a = P - 1$ in $Z_p$. The subgroups generated by a will be $\{1,a\}$.
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### Sharing a secret key between many users

I would like to know if there is any security issue in sharing a secret key (of an asymmetric cryptography) between several users. I know that this secret key is no longer "secret", so it's no longer ...
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### Encrypt a file for multiple persons with different keys?

I thought a problem and want to ask if there's a more elegant solution. The scenario: A company with a fileserver, which hosts encrypted documents. The files need to be accessible by about a dozen ...
384 views

### Why are there only positive value points on an elliptic curve?

I read about elliptic curve cryptography $E$ over $Z_p$ where $p$ is prime number and $G$ is a base point on the curve. I noticed the points resulting from multiplication e.g. $2G$,$3G$,.....,$(N-1)G$ ...
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### Why can't I use ECB with some obfuscation for transient RAM?

I understand that ECB does not hide data patterns well. But my understanding is that it cannot be broken to "know" the underlying message. If that was the case, why can't ECB be used with some ...