# All Questions

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### Test framework for hash functions for collision resistance?

I have two questions about the assessment of collision resistance in hash functions. Given a hash-function what would be the next step to inquiry about it's collision resistance / probability of ...
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### How can I calculate the size of an encryption key?

I have encryption algorithm that has two variables are used as encryption key. How can I calculate the size of the encryption key. I will show an example of what the variables can be: ...
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### Storing salts and iteration number?

I have a function that derives two sub-keys from one passphrase using PBKDF2 one which is used as a encryption key the other for HMAC generation, because these two sub-keys will need to be regenerated ...
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### How can I prove CPA secure by using a new scheme gen,enc,dec from GEN,ENC,DEC?

Given public key encryption scheme $(gen; enc; dec)$, we now construct a new scheme $(Gen; Enc; Dec)$ as follows: The key generation algorithm $Gen$ is the same as $gen$. Each ciphertext for a ...
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### Do OpenPGP SmartCards have the same or better security than an air-gapped machine?

Are OpenPGP SmartCards, such as the OpenPGP SmartCard V2, suitable enough to have secure communications? Meaning, if I connect my smart card to my Mac which is connected to the internet and always ...
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### The number of surviving key after “Meet in the middle stage” in 3-subset MITM attack

In 3-subset Meet in the middle attack, how can we calculate the number of surviving key after meet in the middle stage? and how can we calculate the complexity of Key testing stage? I have read about ...
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### recommendation to see documentaries about history of cryptography

Can anybody recommend any good documentaries which go into some history about cryptography and state of cryptography as of date ? I am not asking for favorites or subjective good documentaries but ...
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### Franklin-Reiter related message attack m2 = a(m1)+b

As shown in their paper, https://www.cs.unc.edu/~reiter/papers/1996/Eurocrypt.pdf, if one is given an equation relating the two messages m1 and m2 as well as other information one can crack both the ...
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### Is it possible to add OpenSSL engine for a block algorithm with different input and output block size?

I need to add a new symmetric cryptography algorithm to OpenSSL, and I thought that the best way to do it is via its engine API. This algorithm will later be used by an application via the OpenSSL ...
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### Crytosystems used to generate public key certificate

Where can we find the cryptosystems used to generate public key certificate? Are the cryptosystems under the signature algorithm and signature hash algorithm? Do I need to analyze the packets ...
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### Multi-round Transposition/Playfair as a secure hand cipher in the computer age

Given that computers can be easily compromised, there is a need for a hand cipher that can withstand computer attack. Clearly the traditional hand ciphers fail. One time pads work. They also have ...
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### How good is middle cube method with jumbled digits?

I had to make my own prng for a stream cipher for an inter school science project (I am mentioning that a lot). So I thought of cubing the seed instead of squaring it (like in the middle square ...
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### Is Paillier cryptosystem commutative?

Is Paillier cryptosystem commutative? If not, how can we construct an oblivious decryption protocol based on Paillier?

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