All Questions

5 views

How is a hash function that implements random oracle model collision resistance?

ROM is considered as collision resistance. Does ROM assume there is an infinite set of output, or assume the output set is always larger than the input set? Bcoz by pigeonhole principle, ROM is ...
574 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 ...
32 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'...
8 views

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 ...
549 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 ...
77 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 ...
9 views

Fix timestamp of self signature on PGP public key [migrated]

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 ...
20 views

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 ...
36 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'...
15 views

What is bounded-retrieval model?

What is bounded-retrieval model in cryptography? How is it related (or apply) to leakage-resilient cryptography?
126 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 ...
21 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 ...
276 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 ...
439 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?
415 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 ...
34 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 ...
48 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?
43 views

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 ...
74 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 ...
34 views

How do I decipher a text using a repeating one-time pad?

I have an encrypted message that is 582 characters long. I know that: It is in hexadecimal It has been encrypted using a one time pad The pad's length is exactly 50 characters When the pad reaches ...
25 views

Do RSA keys contain a checksum mechanism? [duplicate]

I'm new to cryptography, and I was making an experiment a few minutes ago, but I want to have some deeper knowledge about RSA public and private keys. I have a set of keys One begins with ...
26 views

Efficiency of oblivious algorithms vs non-oblivious algorithms

Recently, plenty of researchers are looking at designing efficient data-oblivious algorithms. Roughly speaking, an algorithm is said to be data-oblivious if its data access patterns are independednt ...
30 views

Are any of the practical implementations of ORAM being used in a real world system?

The concept of Oblivious RAM (ORAM) was first introduced by Oded Goldreich and Rafail Ostrovsky in 1996. However, in the past 5-10 years there has been a surge in the amount of research that looks ...
49 views

How to deniably send a value

Alice has a single bit of information, b, that she wants to send to Bob (over an unalterable but possibly-monitored channel) but in such a way that without the ...
19 views

Does changing an encryption key make an application unusable [on hold]

I have a small piece of basic PHP code that adds new users to a database. It was working fine yesterday but this morning I read something about encryption and realized I hadn't changed the encryption ...
179 views

Perfect Forward Secrecy in MTI/A0

Would the property of perfect forward secrecy still be achieved in MTI/A0 for a session key that was established between C and D when one LL-key aD is revealed so that both LL-keys aC and aD are ...
78 views

Finding all polynomials up to a given degree to generate a bit sequence

Consider the following bit sequence: 00100000110 Using Berlekamp-Massey algorithm we can find the following minimal degree polynomial: $P(x)=x^6 + x^5 + x^4 + 1$ Now, is there a way to find all ...
56 views

What makes an open source encryption algorithm safe?

Take for example the popular AES algorithm where we have a combination of substitution, shift row, mix column, and add key steps involved in encrypting plain test. All of the mathematical operations ...
2k views
+100

Signal vs Telegram in terms of protocols?

Some time ago, the question was asked in chat, why MTProto (Telegram's protocol) is supposedly worse than Axolotl (Signal's protocol) as both protocols have been the inventions of their respective ...
66 views

Who invented the $1^n$ notation? [duplicate]

I am always wondering about the seemingly odd syntax $1^n$ which designates the security strength of a cryptographic algorithm. Who invented this (odd) syntax and what was the reason for inventing ...
63 views

In many cryptographic games, the adversary doesn't seem to be parameterized by the security parameter.‡ Are such games equivalent to variants in which the adversary is parameterized by the security ...
44 views

What is the non-programmable random oracle model?

I would like to know the difference between the random oracle model and the non-programmable random oracle model. ​ What is the difference?
383 views

Are there key-derivation functions that are safe to use in parallel on the same secret?

I'm considering using a key-derivation scheme for generating multiple keys from the same user secret. It is important that given all but one of these derived keys, it is not feasible to calculate the ...
89 views

Importance of round complexity in determining the efficiency of an MPC protocol

Literature has different ways of specifying complexity of an MPC protocol: computation complexity that measures the number of (assumed primitive) operations performed by all the parties; ...
16 views

jpbc Element compare [on hold]

I want to compare an element of jpbc.Element produced with another element,produced later.If am inserting the first element to mysql db ,which datatype i will use for an element of type {x=...
136 views

Any benefit to writing a message as a mix of 2 languages before encryption?

For example, imagine a message that is a mix of Japanese and English words; Japanese in unicode, English in ASCII. Japanese doesn't use spaces between words. The sentence structures, anything ...
75 views

Is it possible to test implementation for side-channel attacks?

When it comes to implementing cryptographic algorithms, there seems to be a big focus on the difficulty of doing so without introducing the potential for side channel attacks and the knowledge ...
71 views
+100

culling equivalent Enigma keys for short messages

The following for-loop iterates over all possible keys for an M3 Enigma for three selected rotors: ...
21 views

How to decrypt the below encrypted messages? [on hold]

My friend was experimenting with the encryption methods (self-made) to encrypt text using ASCII map. He wanted to try this idea whether this encryption can be broken and so shared an encrypted text ...
15 views

53 views

Explanation of cryptographic terminology for newbies [on hold]

I feel like I'm making a mountain out of a molehill here, but I have (what should be) a relatively simple project, but the terminology used all over the Internet is either too simple or too difficult ...
32 views

Dependency of cryptographic protocols on cryptography primitives

To what extent depend cryptographic protocols on cryptographic primitives? Are there cryptographic protocols that can only be implemented with certain cryptographic primitives? If the answer is yes, ...
11 views

Can someone help me decipher this? [on hold]

I have absolutely no idea what this is or how to decipher it. Could you either do it... or help me learn how to? ...
33 views

Found weil pairing. Index Calculus method on the results of weil pairing

Consider Elliptic curve with p = 59, A = 1, B= 0, P = (25,30) and Q=(35,31). So I tried to solve this using MOV attack. The torsion point for them E[5] is R(-25,30i) where is sqroot -1 Chosen two ...
In IBE schemes, the system parameters are $(q, \mathbb{G}, F, \hat{e}, P, Q, T, H_1)$. I don't know $\hat{e}$. For example, in type A pairing… ...