All Questions

107 views

Is this a valid “fix” for deterministic encryption in encrypted databases?

It appears (after doing some light research) that for encrypted databases to be practical enough to be usable, deterministic encryption is required, specifically with regard to the type of encryption ...
93 views

Negative exponents in Shoup's threshold RSA?

I'm trying to implement threshold RSA operations, starting with decryption based on Peeters, R., Nikova, S., & Preneel, B. (2008). Practical RSA Threshold Decryption for Things That Think. ...
40 views

With wrong IV at receiver side, the CFB in better than OFB?

Assume the receiver have a wrong IV (initialization vector), in the CFB mode only the first block of plaintext is wrong but in OFB mode the second and all blocks will be affected. Is that correct? ...
225 views

Why isn't CTR mode (counter mode) used more often?

For the CTR mode, the design is good for parallelization, yes, it seems the benchmark of the program downloaded from crypto++ proves that on an Intel I7 CPU. My question is that as most of CPU on ...
51 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 ...
230 views

How are the AES inverse S-Boxes calculated?

I would like to know, how to calculate the inverse S-box. I followed this link (with affine transformation first, then multiplicative inverse), but the result is wrong. For example, if I use the value ...
81 views

Hardness assumptions on composite order bilinear groups [closed]

I am not at all knowledgeable in elliptic curve cryptography. So, here lies a couple of questions that I failed to find answers for to my satisfaction. Is there any known Type-III bilinear pairing ...
76 views

Is there a strong cryptographic reason for GCM's 2^39 - 256 bit limit?

In reading through the original GCM specification (McGrew & Viega '05), the composition of the 128 bit Initialization Vector as a concatenation of a 96b nonce and a 32b unsigned wrapping counter ...
42 views

Is there a strong cryptographic reason for GCM's 2^39 - 256 bit limit? [duplicate]

In reading through the original GCM specification (McGrew & Viega '05), the composition of the 128 bit Initialization Vector as a concatenation of a 96b nonce and a 32b unsigned wrapping counter ...
44 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 ...
133 views

Why can't you just clone encrypted data and use it?

Let's take a contactless card for example (one for public transport lets say (i.e. MiCard)), the data is encrypted on the card and encrypted on the reader as far as I know. So how come somebody who ...
143 views

In ECC, how do I prove that point addition is commutative?

I am studying elliptic curve cryptography and this question is related to the commutative property of point addition operation. Point addition $P_3(x_3,y_3)$ of two points $P_1(x_1, y_1)$ and ...
80 views

Proving that an encryption scheme is susceptible to certain attacks

I'm currently trying to prove the following: Where p is a prime number of cryptographic size, prove that: e(m) = am + b (mod p) where a and b are private is open to a known plaintext attack e(m) = ...
106 views

How does BLAKE2 ensure that hash(A) != hash(B) when B = A||0 and both A & B have the same number of blocks?

Suppose I have two arrays : A = a single byte, being zero. B = two bytes, both being zero. B = A||0 (i.e. B starts with A, and differs only by appending a zero byte) BLAKE2(A) != BLAKE2(B) Yet, ...
105 views

RSA: how does it work and how is it more secure than symmetric systems

Before starting the question, I know that RSA is naturally a key exchange cryptosystem rather than an antilogarithm fully implemented for encrypting and decrypting data since the length of the secret ...
12k views

Decrypt files with original file CTB-Locker [closed]

I have problem called CTB-Locker. It encrypted all of my files on computer and since I have lot of documents that are very important I am in problems! As I read online CTB-Locker uses "elliptical ...
96 views

Will current encryption always remain secure? Is there mathematical proof?

Current encryption algorithms, such as AES, RSA, elliptic curve, etc. work based on known mathematical problems. I am specifically interested in the RSA. Will such security always remain secure? One ...
79 views

Is it a variant of Strong RSA assumption?

Informally, the hardness of RSA/Strong RSA assumption lies in the hardness of factoring a large composite number $N$ having two large primes as its factors. If RSA modulus $N$ is a prime number, then ...
34 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 ...
42 views

Is it possible: Derived key based on variable number of private keys?

I have a MySQL database that I want to encrypt with AES_ENCRYPT() and have to provide access to a variable and possibly changing number of users. Is it possible to derive an encryption key based on a ...
169 views

Achieving 32-bit verification code with 16-bit CRC? [closed]

I am programming an embedded chip that has a hardware 16-bit CRC module. I have to protect some data bytes $d_0,d_1,...,d_{n-1}$ against corruption caused by sudden loss of power; a 32-bit CRC would ...
57 views

What is contained in a RSA key file? [duplicate]

Consider a RSA key file like this: ...
106 views

Spritz cipher sponge function capacity

Rivest and Shuldt proposed a new sponge like cipher algorithm called Spritz: http://people.csail.mit.edu/rivest/pubs/RS14.pdf In this paper they say that the strength of the cipher is related to the ...
62 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 ...
130 views

Why is factoring $p-1$ easy when $p$ is a safe prime?

A paper states: [...] $(p,g,y)$ is a correct ElGamal public key if $g^x=y\pmod p$. To verify this the order of $g$, and thus the factorization of $p-1$, is needed. This is easy for safe primes ...
36 views

Combined message separation

I have two ciphertexts, I suppose that its RC4 with reused key. I have XORed both ciphertexts and obtained message containing combined cleartexts. I suppose that the underlaying messages are written ...
21 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 ...
80 views

ElGamal and Schnorr groups

As I gather, a normal practice for choosing a cyclic group for ElGamal key generation is to find a safe prime $p$ and use a multiplicative cyclic group with modulus $p$ and order $q = (p-1)/2$. ...
171 views

Finding strong primes

Wikipedia lists the following conditions for a prime to be strong: $p-1$ has large prime factors. That is, $p = a_1 q_1 + 1$ for some integer $a_1$ and large prime $q_1$. $q_1-1$ has large prime ...
61 views

Is it possible to perform one-way Diffie-Hellman MITM?

Here's something that is bugging me recently: suppose that me and my friend establish an OTR session and - as a result of that - DH key exchange is performed. My friend verifies my key, but I cannot ...
125 views

How much work is required to detect multiple collisions for a hash function?

Assume an ideal hash function of output size n bits, detecting one collision requires approximately 2^(n/2) evaluations of the ...
28 views

Security issues for integrating AAA and OTP services [closed]

What are the main security issues for integrating AAA and OTP services. In our organization with about 1000 clients, we want to integrate the services. What are the main security issues about the ...
62 views

Should the nonce passed to GCM be authenticated?

This answer recommends authenticating the IV with HMAC when using AES and then HMAC. Since AES-GCM provides authentication too, should the external nonce passed to GCM be authenticated separately ...
60 views

display an image encrypted with ECB [closed]

On wikipedia there is an example of a picture encrypted with ECB: http://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Electronic_codebook_.28ECB.29 I just wanted to know how an encrypted ...
90 views

Security aspects of using a global values as nonce and additional data for AES? [closed]

is it a good idea to use global values as nonce / additional data? What problems can occur? What should be take in account when we deal with such parameters for encryption. Thanks
129 views

Simple message authentication code

I used to figure that message authentication codes function like digital signatures: a hash of a message is calculated and then encrypted with a secret key. To verify the authenticity of a message, ...
99 views

I understand that by definition one-time-pad keys cannot be reused but I was thinking about the case where it is used to send random data and couldn't find anything on the subject so here is my idea: ...
141 views

How does RSA padding work exactly?

I've read everywhere online and people say plain text RSA is very unsafe. To make it safe you pad it but no examples are shown anywhere on how to do it. It's explained that random data is added to the ...
66 views

Diffie-Hellman on infinite groups

The most common groups to be used as examples for the DH protocol are modular multiplication and elliptic curves. But I've realised that the groups doesn't need to be finite, a suitable infinite group ...
53 views

Why the data length is shifted 3-bit in MD4 Java implementation? [closed]

In RFC 1320, It is stated that "A 64-bit representation of b (the length of the message before the padding bits were added) is appended to the result of the previous step. In the unlikely event that b ...
325 views

Is it an example of bilinear pairing?

Consider a bilinear pairing $e: G_1 \times G_2 \rightarrow G_T$. Let's assume, $G_1 = G_2 = G_T = (\mathbb{Z}_n,+)$, i.e. additive group of integer modulo $n$ and $e(x,y) = xy$ mod $n$. Isn't it an ...
252 views

How does cryptanalysis of the Playfair cipher work?

I have a set of Playfair-enciphered data that I'm trying to crack without the key. I know I need to analyse bigrams; I've currently worked out what decrypts to th, ...
547 views

Secure way to encrypt and decrypt a folder on Mac or Linux? [closed]

I am looking for a way to securely encrypt files on Mac and Debian. OpenSSL comes pre-installed on Mac OSX and Debian/Ubuntu. Therefore, is this a safe/recommended way of encrypting individual files? ...
71 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 ...
128 views

Is RC4 +XOR secure for small data?

I need to encrypt transmission between my device (with AVR processor) and base. I create packet data - it will be encrypted into string: ...
64 views

wireless network security protocol

In network security, encryption and integrity done by the same algorithm that is AES-CCM in that MIC generated by CBC-MAC and encryption done by CTR mode. So suppose I want to do encryption with any ...
111 views

BEAST attack confusion

I understand that BEAST is a CPA using javascript injected onto the browser's webpage. Apparently the thing that BEAST exploits is the fact that the IVs are predictable. What I'm confused about is why ...
100 views

Why can't I use ECB with some obfuscation for transient RAM?

I understand that ECB does not hide data patterns well. But my understanding is that it cannot be broken to "know" the underlying message. If that was the case, why can't ECB be used with some ...