# All Questions

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### Is it OK to reseed a Deterministic Random Bit Generator from itself?

I want a deterministic PRNG for simulation purposes, and I don't want to have to worry about spurious correlations like those the DMCT is designed to protect the Mersenne Twister against. So even ...
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### Is there a security problem with this prime generation algorithm?

I am facing the following algorithm to generate an RSA public key: ...
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### Identity-based proxy re-encryption using different system parameters

I am wondering if there is an identity based proxy re-encryption scheme (such as the Green-Ateniese scheme https://eprint.iacr.org/2006/473.pdf) that converts an encryption computed with ID1, system ...
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### Fixed-prefix IV in CBC mode

I know the Initialization Vector needs to be unpredictable. Does it apply to the IV as a whole, or to every bit in the IV? I have multiple devices with poor entropy sharing the same key and I want to ...
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### Best/average/worst-case complexity for cryptography

I understand that the complexity of a problem can be measured by it's best-case, average-case, or worst-case complexity. Am I correct in thinking that, for cryptographic purposes, each of these is of ...
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### Difference left-or-right CPA security, IND-CPA security

I am trying to understand the notion of left-or-right-CPA (LOR-CPA) security for private-key encryption schemes introduced in my lecture. If I understood it correctly so far, the only difference to ...
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### What about using AES-ECB with random IV?

Let P1P2...Pn be n blocks plaintext, and M0 be a random IV. Then a n+1 blocks message M0M1...Mn can be constructed by setting Mi+1 = Mi xor Pi+1. Finally, we use AES-ECB to encrypt this message. Is it ...
2k views

### How to publish a cipher (concept)?

In the last months I was searching for a subject for my bachelor thesis. I came up with an idea for a new cipher concept that works by combining already known techniques in a (hopefully) new way. So ...
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### How to deal with different setup in Multikey FHE?

The scenario : using a Multikey FHE scheme, let's say LTV-FHE scheme, parties delegate the computation of some function to the mighty cloud. In LTV-FHE scheme the parties generate their keys and ...
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### What is the threat to a PKI when the root CA certificate is generated using SHA1?

We have thousands of servers that have been issued certificates signed by our CA using SHA256 but the our root CAs own certificate was generated using SHA1. Assuming SHA1 is no longer secure for our ...
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### Could a key derivation function be used to encrypt data with a weaker key?

To allow the key to be more easily remembered. Example: To encrypt a hard drive without having a remember a key with 128 bits of entropy. From what I find they seem mostly used to hash passwords so ...
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### Hash + Salt v. Hash + Encryption

I was wondering if using a salt with a hash is more effective than hashing and encrypting your hash.
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### Difference between hierarchical and multi level secret sharing

In this paper, the definitions are simply as follows. Multi-Level secret sharing: Higher level participants can help lower participants to get the secret. Compartmented secret sharing: Each level ...
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### How easily could this method of cryptography be cracked? [closed]

Background A couple of years back, in my naivety, I dreamt up a method to encrypt information. The result can be seen on my website, I evidentially thought it was pretty neat and I decided to mix it ...