# All Questions

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### Does CP-ABE have any disincentive to share secret keys

I want to use a CP-ABE scheme to encrypt data to be accessed by multiple unknown (at time of encryption) users. Reading the papers related to CP-ABE, there does not appear to be any disincentive for ...
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### Multiple levels of encryption

Is it feasible to have data encrypted at different levels? I'd like to encrypt an xml database (such as used in www.keepass.info) whereby two keys can exist: Key #1 decrypts the entire database ...
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### Why can you reverse a modulo function when knowing its primes

We are dealing with cryptography in school right now and superficially went over the Rabin cryptosystem with the (apparently usual) example of p=7 and q=11 etc (we didn't do RSA). I understand that ...
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### Exactly how slow is asymmetric encryption?

I'm currently doing a project on RSA, and have just come across this website. https://www.namecheap.com/support/knowledgebase/article.aspx/798/67/what-is-an-rsa-key-used-for On here, it says that ...
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### Which is better? Serialize and then encrypt or Encrypt and then Serialize

Let say in a simple Java program, Considering all the facts, like security and performance, Which is the best way to follow. I tried searching for a answer but proper answer is not out there.
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### security definition

I am new in cryptography and I saw this question in a book. I really don't know what this question means and what is the answer of it(it's not my homework etc. but I'd love to know the answer of ...
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### secure PRF or not

I am new in Cryptography and I saw this question in a note I solved it but I'm not sure about my answers. Let $F : \{0, 1\}^n × \{0, 1\}^n→ \{0, 1\}^n$ be a secure PRF (i.e. a PRF where the key ...
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### RSA time function

I am doing a paper on textbook RSA (highschool-level). I am explaining and proving the significance of the public key exponent in time and security. So far, I have encrypted a constant message with a ...
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### attack on modified DES

any idea for attack on this modified DES? Each round sub-key is 32 bits long, and the round function simply $XOR$s the round sub-key with the input to the round (i.e. $f(k, R) = k_i ⊕ R)$ . For ...
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### Which gives better deterministic encryption SIV or Plain ECB mode?

Lets say , if we encrypt a plain text message $msg$ with key $key$ in below two ways. Which is the below would give better deterministic encryption and why ? AES-ECB($key$ , $msg$) SIV($key$, NIL , ...
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### Encryption and HMAC key derivation

I'm deriving keys from a user-supplied passphrase for symmetric encryption using AES-256 in CBC mode with a HMAC for authenticity/integrity. My key derivation function currently looks like this: ...
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### Execution time RSA [on hold]

I am doing a paper focusing on the public key exponent in textbook RSA. However, I need to know the time complexity for encryption time. I have heard both $O(\hspace{.02 in}\log_2(x))$ and $O(x^2)$ as ...
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### Reference AES-NI assembler code for AES-128-GCM? [closed]

I want to implement AES-128-GCM in assembler using Intel AES-NI instructions. I have found reference code in the Intel AES-NI Whitepaper but I don't see code for the GCM mode there (or indeed any use ...
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### Elliptic Curve Blind Signature Implementation

I have seen this prior post: Elliptic Curve based blind signature implementation Currently I'm sizing up how difficult it would be to attain Elliptic Curve Blind signatures for an application I'm ...
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### How to decrypt the PBKDF2 Algorithm [closed]

can you please brief me about PBKDF2,how to decrypt the PBKDF2 algorithm.
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### Bouncy jdk 1.51 Serpent KAT tests vs Nessie vectors

Having a little trouble getting Nessie vectors working with the Bouncy Castle SerpentEngine. Do the Nessie vectors require a mode or some pre-processing? Nessie Serpent 128, set 1, vector 0 reads: ...
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### Is there a way to do single key-pair asymmetric encryption?

All of the information on asymmetric encryption I can find uses key-exchanging to get a mutual symmetric key. What I am trying to do is encrypt a message with a public key and have it only readable ...
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### Why is the IV passed in the clear when it can be easily encrypted?

The initialization vector (IV) is exclusive or'd against the plain text before encryption for the first block sent in order to prevent an attacker from learning that duplicate message blocks are being ...
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### Breaking a Modified Caesar Cipher

Does anyone know of an efficient way of breaking a modified Caesar cipher (where the key is a set of numbers (the amount of shift) that is repeated throughout the plaintext, e.g. {1,2,3,4,5}) via ...
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### Decipher APDU for OpenPGP smart card applet [migrated]

I'm implementing data deciphering into my Java application using javax.smartcardio APIs. I'm using Yubikey NEO smart card element. I managed to: Select OpenPGP applet ...
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### State of the art techniques for Anonymous Authentication?

What are the state of the art techniques for Anonymous Authentication? What are the most popular ones? The problem domain I am considering is with respect to different users accessing cloud content; ...