0
votes
0answers
44 views

Key length requirement in a simple XOR implementation

I don't have much previous experience at all with cryptography, this is pretty much the first time I've tried anything similar. I'm trying to implement an extremely simple XOR encryption system in ...
0
votes
0answers
27 views

Transport SA bundled inside a tunnel with encryption applied before authentication?

For IPsec I am considering different formats of ESP encryption and authentication. I am not sure what happens with "Transport SA bundled inside a tunnel with encryption applied before ...
0
votes
0answers
44 views

What work goes into creating new asymmetric cryptosystems?

It's seems to me that it is rather easy to create a symmetric encryption algorithm (though not necessarily a secure one). They're a dime a dozen. The number of asymmetric encryption algorithms ...
0
votes
0answers
41 views

Separate keys for encryption and MAC? [duplicate]

I use HMAC(ciphertext)+ciphertext for authenticated encryption. The same key is used for both MAC and encryption. Is that right? Is using separate keys for MAC and encryption necessary or any good? ...
0
votes
0answers
21 views

Looking for an adjustable compute bound decryption function

I'm looking for a way to decrypt data, but make it require varying amounts of CPU power to do so. Maybe this could be illustrated as e(m) = m' and ...
0
votes
1answer
126 views

Problem with testing MD5 collisions

I am trying to test MD5 collisions presented in “Collisions for Hash Functions MD4, MD5, HAVA” (PDF) by Xiaoyun Wang, Dengguo Feng, Xuejia Lai, Hongbo Yu; 2004. I wrote a PHP script to test it, but ...
0
votes
0answers
52 views

What is the best authentication logic to analyze RFID (randomized hash-lock) authentication protocol?

What is the best authentication logic to analyze RFID (Randomized hash-lock) authentication protocol, (Ban logic, GNY logic, SVO logic, VO logic, AT logic) or another one?
0
votes
0answers
38 views

AES mode scheme feedback [duplicate]

I've been studying encryption on a hobby basis, and wanted to know if I got this basic cypher construction right (this is another experiment, see the AES ECB experiment thread earlier). Encryption: ...
0
votes
1answer
110 views

DH and PKI for KeyExchange

My question is fairly simple. I have more than two nodes which needs to communicate very efficiently from computational point of view. One of the nodes can become a coordinator between the nodes. ...
0
votes
1answer
57 views

One-one correspondance complete function

I am reading the paper by John B. Kam and Georges I. Davida (1979) titled Structured Design of Substitution-Permutation Encryption Networks. On page 749 it reads ...
0
votes
0answers
34 views

Pseudorandom function and hash function [duplicate]

What is the difference between a pseudorandom function and hash function ? I have already read the answer in this link What is the difference between a hash function and a pseudorandom function? but ...
0
votes
0answers
74 views

What do you think about this message encryption?

I am currently working on my diploma project, a high security NFC door lock and need to exchange very sensible data. That's why I thought of PGP encryption, which is as far as I know one of the ...
0
votes
1answer
50 views

GCM implementation

I want to write GCM implementation myself (only for research purposes). So far, I have successfully written CTR implementation (for AES), but now I ran into few problems with GCM. If I'm not wrong, ...
0
votes
1answer
153 views

How does knowing the factorization of N can help to obtain the secret?

Assuming $x=a^2 \pmod n$ and knowing $x$, $p$, $q$ how is it possible to obtain $a$?
0
votes
1answer
35 views

Hill Cipher the point of a known plaintext attack question

Is the point of a known plaintext attack on a Hill Cipher to get the matrix key?
0
votes
0answers
92 views

Substitution-permutation network

Can anyone in 6th grade English explain the steps in the Substitution-permutation network algorithm or just point a link that does so? (which is included in many of the top modern algorithms) ...
0
votes
0answers
65 views

BGV FHE scheme parameters

In their paper presenting the BGV scheme, the authors mentioned in section 4.4 that, for the RLWE variant, the ring degree d, dimension n and noise distribution do not necessarily vary with the ...
0
votes
0answers
57 views

How does double-encryption work with a client server model

With mobile applications like Accompli (now the base for the Android Outlook application), credentials are stored. Reading from the Accompli website: Each user’s credentials are double-encrypted ...
0
votes
0answers
52 views

Full Domain hash library

I need to know if any of the well-known crypto libraries (openssl, crypto++) supports full domain hash function. If not, what library I can use?
0
votes
0answers
53 views

Encryption - How to find $\sigma$?

Alice communicates with Bill using an encryption system of type Feistel. Specifically, each block has a length of 128 bits, the algorithm has 4 rounds and the common secret key of Alice and Bill is ...
0
votes
0answers
61 views

Find a polynomial time algorithm for the following problem

Let $p$ be a prime number and let $c \in \mathbb{Z}_p$ and $e \in (\mathbb{Z}/(p-1))^{\ast}$. Put $c \equiv_p m^e$. Find a polynomial time algorithm that given $p$, $e$, and $c$ will compute $m$. I ...
0
votes
1answer
65 views

Crack RSA with additional information [duplicate]

Suppose $N=3953$, Alice encryption key is $e_A = 337$ and bobs is $e_B=23$. Eve happens to know the corresponding decryption keys, $d_A=3385$ and $d_B=2663$. Can I use this information to find the ...
0
votes
1answer
44 views

ECIES with AES-GCM

The Elliptic Curve Integrated Encryption Scheme (ECIES) describes how to derive a "temporal" key, encrypt a message (eg. using AES) and creating a MAC. However, from my understanding using AES in GCM ...
0
votes
0answers
60 views

Affine transformation in finite field SubBytes

Can anyone please explain how this computation was done? I picked it up from How are the AES S-Boxes calculated? The affine transformation is as follows. The input bits are multiplied against the ...
0
votes
0answers
69 views

Pseudorandom number generators based on hard problems in mathematics

I know that Dual_EC_DRBG's security is based on the ellitpic curve discrete logarithm problem, Micali-Schnorr is based on the difficulty of factorization, and MQ_DRBG is based on multivariate ...
0
votes
1answer
226 views

SHA-512 Length Field - What is it?

If I am using SHA-512 on a message and need to determine the padding field and length field, how do I determine the length field? I think I understand the padding, but not the length field. For ...
0
votes
1answer
63 views

Hashing - Digital Signing and Trivial Stretching

Two very basic questions: 1. Digital Signing Why is it not possible to just simply replace the hash value from the request? Examples: ...
0
votes
1answer
49 views

Is the key deducible with AES CTR when we know about the plaintext, IV and the ciphertext? [duplicate]

Simply as stated, with AES running in CTR mode, can somebody work out the key (without brute-forcing) given we know about the plaintext, IV and also the ciphertext. Assuming we also know about the ...
0
votes
0answers
18 views

Can a tree hash with leaf-size of 1 byte support verification of content with elided ranges, at a cost of at most 2 supplied internal-node hashes?

Perhaps someone can confirm my intuition: A tree hash with leaves of size 1 (for example Blake2 in a tree-hash mode) would of course not be very efficient. But it seems that it might be a suitable ...
0
votes
0answers
67 views

Strategies for securing public key storage on software

I´m kind of new in this so I apologize in advance for any noob mistakes (feel free to point it out) We are developing a licensing mechanism on our software, and I would like some advice. The ...
0
votes
0answers
76 views

Deriving a decryption equation

Consider a very simple symmetric block encryption algorithm, in which 32-bits blocks of plaintext are encrypted using a 64-bit key. Encryption is defined as C = (P⊕KL)⊗KR where C = ciphertext; K = ...
0
votes
1answer
63 views

Self changeable key [closed]

If key changes itself when it send/receive message what would be could breaking method? So: $E: m×k$ in which $k$ is last generated key $D: c×k$ in which $k$ is last generated key $k{_n} = ...
0
votes
0answers
46 views

Key establishment protocols other than Diffie-Hellman

Are there any key agreement/exchange/establishment protocols which are NOT based around the Diffie-Hellman protocol or handshakes using public key cryptograaphy? DH seems to form the basis of this ...
0
votes
0answers
42 views

Security comparison of the following PBE algorithms - PBKDF2WithHmacSHA1 Vs PBEWITHSHA256AND256BITAES-CBC-BC

Which among these conform to the PKCS#5 OR PKCS#12 standards ? Are they JCE compliant - In other words which providers have implemented them in a JCE compliant manner ? How do they fare in terms of ...
0
votes
0answers
44 views

Are Barreto-Naehrig Curves suitable for pairing-based cryptography?

If Barreto-Naehrig Curves are suitable for pairing-based cryptography, can I use the library available at Optimal ATE Pairing?
0
votes
0answers
35 views

How does CTR-ESSIV work ? (cryptsetup Linux)

I'm using Wikipedia and Handbook of Applied Cryptography as references. I know that ESSIV generates an initialization vector (IV) by combining a hashed key with the sector number. However, I only see ...
0
votes
0answers
43 views

RSA algorithm in this doesnt (ever) give right decryption [duplicate]

Lets consider p=47 q=57 msg=3 n=p*q=2679 ф(n)=2576 now e=11, and inverse of e is 1171 modulo ф(n) y=msg^e=333(mod n) ///Encryption y^d=1131(mod n) ///Decryption but this is not original message ...
0
votes
0answers
56 views

compression with codebook and Cryptography

a question about the difference between code book based compression method and key based cryptography. As I know Crypto != Compression. The Shannon said Crypto is try to reduce the information of ...
0
votes
0answers
91 views

Python implementation of a blind signature scheme which doesn't involve RSA

RSA seems a bit creepy after the Snowden revelations and i'm looking for a simple python based blind signature library to fiddle around with. So far i've been unable to find anything. What am i ...
0
votes
0answers
53 views

Decrypt a message which is encrypted using XOR? [duplicate]

This is a puzzle asked in a contest. Given that encryption , decryption happens as per following rule/code: ...
0
votes
0answers
23 views

Kryptos K2 keyword derivation [duplicate]

So I've been doing some reading on Kryptos, and to be honest the keyword for K2, ABSCISSA, has a pretty weak derivation. (The method using the eee's). Isn't there a better way to come to that? I dont ...
0
votes
1answer
63 views

Non-repudiation and digital signature of a dishonest participant

Let's assume a dishonest Alice who sends, encrypts & digital signs a message to Bob. Bob stores the decrypted message and the digital signature in a database. However Alice is a bad girl and ...
0
votes
0answers
23 views

Reducing key shares in Damgård-Dupont threshold RSA

I'm working on understanding and implementing Damgård, I., & Dupont, K. (2005). Efficient Threshold RSA Signatures with General Moduli and No Extra Assumptions. Public Key Cryptography-PKC ...
0
votes
0answers
27 views

Proving the complement property of DES? [duplicate]

I'm trying to show that for a given plaintext (P), key (K), and cipher (C) in the DES algorithm: ...
0
votes
0answers
42 views

Problem in understanding Blakley's Secret Sharing Scheme

I need to implement Blakley's Secret Sharing Scheme. I have read below mentioned two research papers but still unable to understand how to implement it. Safeguarding cryptographic keys Two Matrices ...
0
votes
0answers
43 views

Is signing a message just encrypting it with private key? [duplicate]

I have a simple question, When I sign a message (in RSA) does the program encrypt the text with my private key? Because I can decrypt it with my public key. Yes or no. Is signing a message just ...
0
votes
1answer
33 views

Cipher for human interpretation [duplicate]

Please suggest algorithms to encrypt and decrypt text messages that can be easily performed by human in a considerably short time. It doesn't have to be really secure, but sufficient to fool ...
0
votes
1answer
58 views

Converting a number to a member of a multiplicative cyclic group

I am currently trying to make an implementation of the ElGamal encryption for educational purposes. As I understand it, when using the encryption with multiplicative cyclic groups, one generates a ...
0
votes
0answers
18 views

Data anonymization and search with wild-cards

Broadcast encryption technique proposed by Water et al. http://www.slideserve.com/nairi/revocation-systems-with-very-small-private-keys takes a leap from earlier schemes as it provides smaller user ...
0
votes
0answers
64 views

chameleon signature vs regular signatures

I am trying to understand the practical usage of sanitizable signatures particularly on Chameleon Hashing and Signatures. Chameleon hash, or trapdoor function allow parties with the knowledge of the ...

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