# All Questions

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### For hardware encryptions, is it possible to know the key by analysing the hardware?

For example, Square reader uses hardware encryptions when swiping credit cards. Is it possible to know the key that is used by the hardware encryption cipher by analysing the hardware circuitries? ...
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### Is it worth hiding an AES encrypted text string in a PNG image for better security?

I need advice as to whether it is worth the extra "security" and processing of an AES encrypted text string to be hidden in a PNG image as opposed to an AES encrypted text string to be saved in a ...
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### For the scrypt HMAC storage format, why run the input of the hash and the hash itself into the HMAC

Generally if the body is hashed, why provide the body and the hash as input into the HMAC. Instead wouldn't the same security be achieved by hashing the body and providing only the hash as input into ...
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### Computing the padding of MD5

So I'm reading this question to learn more about length extension attack, and I want to make sure I understand the basics of padding. It says in the post that given the hash and the length of the ...
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### Binary equation with encryption

I'm trying to test the ring signature scheme proposed by Rivest Shamir and Tauman in the famous paper "How to leak a secret". One of the step consist in 4) the signer solves the following ring ...
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### Security of SRP-6a against impersonating server choosing small/wrong N

I'm looking at an implementation of SRP (Secure Remote Password) that essentially follows the Stanford documentation (http://srp.stanford.edu/design.html). I'm worried about one aspect though: In the ...
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### How to derive a key from an existing AES key?

Currently, the code I am staring at uses the CKM_EXTRACT_KEY_FROM_KEY mechanism. That has been disabled in our hardware module, so I need a different mechanism to ...
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### Why do we require a CSPRNG's output to be indistinguishable from true random?

Everywhere I read, indistinguishability of output from true random is stated as a requirement for CSPRNGs. However nobody bothered to give the rationale for such a strong requirement. Specifically, ...
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### How have MD5 constants been determined?

For instance, the per round shift amounts, ...
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### MD5 SSL Collision Attack

I want to create fake certificate for test purposes. I have read about the http://marc-stevens.nl/p/hashclash/index.php project but I am unable to understand the two files that I have to put as input ...
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### special class of lattices in lattice based cryptography

A special case of lattices in lattice cryptography is that of q-ary lattices. A q-ary lattice L is defined as that in which any vector which consists of multiples of some scalar q is in ...
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### Is it safe to initialize secret keys by just reading /dev/random on Linux?

For a software, I don't want the user to choose weak keys, so I plan to just read the needed number of bytes from /dev/random to create the needed secret keys. Is it safe to do so?
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### Are there MD5 collisions for inputs of different length?

There are many examples of MD5 collisions (some of them can be found here Are there two known strings which have the same MD5 hash value?). But as far as I know two inputs should have the same length ...
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### Can an encryption method be used as a hash function?

As I understand, there are a few requirements for a good hash function. Hard to find any message from a given hash Hard to find any 2 messages which give the same hash A single bit change in the ...

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