All Questions

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any post-shannon symmetric ciphers?

As far as I understand block ciphers use only simple operations to ensure good enough confusion and diffusion levels. meaning there is no math in it. "breaking a good cipher should require as much ...
83 views

Calculating Polynomial Inverse with extended euclid in java

I'm trying to understand the NTRU-PKCS and therefor I wanted to code a naive Version of it. Now my Problem: I tried to calculate the inverse of a Polynomial with an extended Version of euclids ...
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Why is symmetric lightweight crypto only about block ciphers and not about stream ciphers?

Why is symmetric lightweight cryptography only about block ciphers and not about stream ciphers? AFAIK stream cipher implementations cost at least three times less than block cipher ones?
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Does changing the order of the steps within a round affect the security of AES?

I was trying to understand the internal structure of AES (Advanced Encryption Standard) Standard order of steps within a round: Substitute Bytes Shift Rows Mix Columns Add Round Key Substitute ...
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592 views

How do RSA and ElGamal key sizes compare?

I have a rather silly question regarding the comparison of RSA with ElGamal over integers. If you want to compare their performance in the same level of security, does the modulus of both of them need ...
153 views

Prime factorization of 700 decimal digits number

I'm a newbie to encryption. If I create a number 'n' as a product of two prime numbers 'p' and 'q' with the following specifications: 'p' is a fully random prime with 300 decimal digits in length. 'q'...
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A5/2 Ciphertext Only Attack

I've studied that A5/2 could be attacked with cipher-text only, using the Error Correction Code, in order to retrieve the session key. Here's an article I tried to read about it (section 4). (however ...
571 views

How dead is braid based cryptography

Braid groups has drawn the attention of cryptographers for a few years, as a promising platform for post-quantum cryptographic protocols. The security of the proposed schemes mostly relied on ...
81 views

Forgery attack against Textbook RSA with simple redundancy

I know how to forge vanilla Textbook RSA message signatures (easy). I've learnt that by adding a good redundancy to the message, it cannot be forged anymore. How can one add redundancy so that the ...
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Fix timestamp of self signature on PGP public key [on hold]

I accidentally changed configuration of my pgp key while my system didn't have the correct clock. And I uploaded my key to key servers. Now every time I try to download my key from key servers or even ...
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Getting the same two hash values for carved files I found

I am doing an independent study class for computer forensics, I have to carve the images I've been given. After using scalpel I get a .wav file and .asf file both files play the same songs, and they ...
39 views

How does the key size in supersingular isogeny schemes relate to their security level?

I'm looking at the De Feo, Jao, and Plût 2014 paper: Towards quantum-resistant cryptosystems from supersingular elliptic curve isogenies. My understanding of section 3.2 Key Exchange, is that Alice'...
19 views

What is bounded-retrieval model?

What is bounded-retrieval model in cryptography? How is it related (or apply) to leakage-resilient cryptography?
130 views

Where and how to store private keys in web applications for private messaging with web browsers

I am working on a web application enabling users to communicate over private messages which is just one part of the whole system. The main focus during my development process is to protect the privacy ...
23 views

Attacks from releasing decrypted CCM payload before verifying tag

CCM specifies (Section 1.7) that no plaintext data should be released before the MAC is verified. Why is this recommendation given and what attacks are possible against CCM if data is treated like a ...
277 views

PGP String-to-Key specifiers

I've been reading through the PGP Standard and here I'm a little confused. This section is discussing converting string data to a session key. I'm confused about the paragraph in bold. First off, what ...
455 views

Feistel-Network - why wire crossing?

In Feistel-Network, there would be a wire-crossing at the end (for the next round). Which insufficiency would occur, if the wire crossing would be omitted?
419 views

Any real world implementation using message recovery?

During my master thesis I came across RSA-PSS-R which is in my opinion a quite elegant way of saving bandwidth and space using digital signature. But I didn't find any information about any real world ...
1k views

Description of signatures with message recovery (as in ISO/IEC 9796-2 and EMV Signatures)

I'd like to get an overview of how the signatures with message recovery work, especially in case EMV and other smart card systems. Is there a nice overview available without being required to read the ...
37 views

Attacking Scrypt Under Access Pattern Leakage

Could cache-timing channels (such as exist for certain block ciphers) somehow be made use of in order to extract memory-access pattern information if both the attacker and user are NOT in a shared ...
49 views

How to use modes of operation in DES? [on hold]

How to use modes of operation in block cipher with Data Encryption Standard (DES) ? How the Feistel structure properties are achieved in DES when a mode of operation such as ECB is used?
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Ideal way to profile/performance-measure cipher implementations

I have implemented a bit-sliced version of two ciphers (Gibbon-120 and Hanuman-120, both part of the Primates family of ciphers: http://primates.ae/wp-content/uploads/primatesv1.02.pdf ) I now want ...
75 views

Initializing PGP keys by one side

I am using a PGP method to encrypt and decrypt messages shared between users A and B. Upon the start of a message exchange is the initialization of the public and secret keys by both Users. Lets say ...