# All Questions

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### Hash collision resistance of $\mathcal H^\prime(m) = \mathcal H(\mathcal H(m)|m)$

So far as I can find, every method better at producing hash collisions in cryptographic hashes than generic collision search involves finding some metric for the distance between two messages' hashes ...
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### What constitutes a “description of B” for probabilistic encryption as defined in Cryptology 6.3.4?

On page 21 of the Rivest's Cryptology chapter, he defines a trapdoor predicate as a boolean function for which it is easy to choose an x such that ...
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### Special random distribution algorithm

I am implementing ring signatures as a part of an authorization system. Since the number of users could get high enough to make computation on end-user devices infeasible, I am thinking of "...
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### Why should a signature use PSS padding in RSA?

Suppose I send a message using AES (private keys already negotiated securely) and I send a hash of this message using RSA (encrypted with private key) with OAEP to verify the authenticity and ...
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Is it possible to figure out what $arg1 is if I know both$arg2 and $arg3 in addition to <... 2answers 1k views ### Does the secret key used in AES have to prime? I’ve looked around this site and the web quite a bit, but can’t find a definitive answer on whether or not the secret key$k$used in the AES crypto-system has to be a prime number? Or can you just ... 0answers 63 views ### Performance analysis of roaming authentication protocol using pbc library Recently, I have surveyed a few research papers related to roaming authentication protocol for wireless networks. For example: “Efficient Privacy-Preserving Authentication in Wireless Mobile Networks” ... 0answers 26 views ### Is TLS_RSA_WITH_RC4_128_SHA still a secure cipher to use? [duplicate] I have read numerous times that the RC4 cipher itself is considered broken in TLS. Still many websites are using the TLS_RSA_WITH_RC4_128_SHA configuration even to date. Now, I know that sometimes ... 2answers 1k views ### Finding the LFSR and connection polynomial for binary sequence. [closed] I have written a C implementation of the Berlekamp-Massey algorithm to work on finite fields of size any prime. It works on most input, except for the following binary GF(2) sequence:$0110010101101$... 1answer 262 views ### How can the key size be calculated [closed] If the decrypting key is 448, then what is the key size? Suppose I am encrypting a plain text with a key by choosing some random numbers between ... 1answer 229 views ### No of keys used in Triple DES Algorithm I am studying Triple DES. I have got two basic questions. One, why are we following a sequence like encrypt(decrypt(encrypt)); what is the problem using a sequence encrypt(encrypt(encrypt))? Second,... 2answers 407 views ### How to retrieve the plaintext of a substitution ciphertext? So the other day, I was piqued by a ciphertext that was trivially encoded through substitution. Solvable only because we can use our eyes to determine word boundary word detection, etc. Trawling the ... 1answer 290 views ### How does the energy consumption of the SHA-3 finalists compare? I am curious, is there any paper where SHA-3 competitors are compared in terms of energy efficiency? 0answers 165 views ### The advantages of Merkle Signature and One time Signature In Merkle Signature, it also requires one-time signature to be used once for a message. The signature in Merkle scheme is even longer compared to Lamport one time signature. The verifier also has more ... 0answers 76 views ### How to decrypt a text which is ciphered same length key? [duplicate] I have ten piece of ciphered texts. I know that they ciphered with a same-length key. Any idea how I can decrypt the ciphertexts? What kind of algorithms should I use? What are the points of taking ... 1answer 183 views ### Pseudo-random Number generation for Passwords I am looking for a good pseudo-random number generation algorithm for passwords. My scenario is that I have to generate 5K pseudo-random bits from a user-supplied password (6 characters). What are ... 1answer 117 views ### Back up an information as$n$pieces and require exactly$n-1$to recover it Let$X\in \Bbb F_2^p$be some information. How do I create$Y_1,\dots,Y_n \in \Bbb F_2^q$so that having less than$n-1$of the$Y_i$s gives you no information on$X$but having$n-1$of them allows ... 2answers 89 views ### Building cryptographic primitives using additive maps? Suppose we have a one-way function F(x) that exhibits the property F(a + b) = F(a) + F(b). Such a function could be used as a cryptographic primitive, no? 2answers 453 views ### Why is ElGamalEngine in bouncy castle restricting input data to be less than the length of the group parameter p? I am currently using the ElGamalEngine of bouncy castle to implement exponential ElGamal for the purpose of making ElGamal additively homomorphic. To do this i raise the message to be encrypted to the ... 1answer 588 views ### What is the best way to share a shared secret key over HTTPS to be used for HMAC authentication? I am writing an application in Java that will be using SHA-1 HMAC message authentication. From what I understand, a connection over HTTPS is considered secure enough to share a secret key in plain ... 0answers 136 views ### FHE over the integers - Is that paper's scheme known to be insecure against quantum adversaries? I was reading the paper Fully Homomorphic Encryption over the Integers, and started wondering if there is a known quantum attack on their main scheme, because There is an efficient quantum attack ... 2answers 286 views ### Point addition and doubling in Ed25519 (ref10)? I just migrated CodesInChaos' C# port of Ed25519(ref10) to Java, and everything works fine. (I.e. I get the same results for key generation, signature and verification.) Now, I would like to do a ... 2answers 303 views ### Asymmetric key derivation – Who derives the new pub key can't know the new private key I'm looking for a peer reviewed protocol or algorithm that can do this, preferentially I need something based on elliptic-curves cryptography. Alice know the main public key of Bob (B-PUB-1). Alice ... 2answers 160 views ### Size of p in ElGamal cryptosystem? In the ElGamal cryptosystem, I was wondering whether the$m$(message) should be less than$p$(large prime). Because on decryption, we are getting$m \bmod p$. For$m \bmod p$to be equal to$m$, ... 1answer 3k views ### Why is Triple DES not vulnerable to meet in the middle attacks? Consider the Triple DES encryption calculated as: $$C= E_{K_1}(D_{K_2}(E_{K_1}(P))).$$ For a chosen plaintext attack, given plaintext$P$, we compute the result of$D_{K_2}(E_{K_1}(P))$and store ... 1answer 614 views ### Understanding how SHA-512 achieves its design goals The Wikipedia entry on SHA-2 contains a usable pseudocode recipe. In the hope of some deeper understanding, I implemented SHA-256 and SHA-512 from it. This was helpful, but I still don't think I have ... 1answer 94 views ### Can N, q be shared for multiple users when using SRP-6A Is it considered bad practice to use the same N and q parameters for all users in an SRP-6A based authentication system? I know that q MUST be a Sophie Germain prime and N a safe prime, but can they ... 1answer 135 views ### Group Signature Scheme without Opening but with Revocation After reading many papers about group signature schemes, I saw that basically all of them employ the possibility of "signature opening": The Group Manager (GM) can identify any signature made by his ... 1answer 63 views ### Computational Diffie-Hellman problem over the group of quadratic residues Suppose that$N=pq$where$p$and$q$are safe primes.$\mathbb{QR}_N$is the group of quadratic residues which is a cyclic group with order$\frac{\phi(N)}{4}$. Let$g$be the generator of$\mathbb{...
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I would like to know how to extract contents of the password protected WinRar file without the password. I have downloaded that WinRar file from a file hosting website and found out that it was ...