0
votes
1answer
40 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 ...
2
votes
1answer
51 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 ...
3
votes
2answers
350 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 ...
-2
votes
1answer
100 views

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

Consider a RSA key file like this: ...
4
votes
1answer
137 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 ...
0
votes
1answer
75 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
1answer
168 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 ...
1
vote
2answers
41 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 ...
1
vote
1answer
157 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 $q = (p-1)/2$. ...
5
votes
2answers
333 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 ...
2
votes
0answers
76 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 ...
0
votes
1answer
173 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 ...
0
votes
1answer
49 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 ...
0
votes
1answer
89 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 ...
1
vote
1answer
141 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 ...
0
votes
1answer
94 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
1
vote
1answer
257 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, ...
-1
votes
2answers
152 views

Reusing one-time-pad with random plaintext

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: ...
0
votes
2answers
293 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 ...
0
votes
1answer
72 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 ...
1
vote
2answers
1k 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 ...
6
votes
2answers
984 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, ...
-1
votes
4answers
1k 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? ...
0
votes
1answer
272 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: ...
0
votes
1answer
79 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 ...
2
votes
1answer
148 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 ...
0
votes
1answer
108 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 ...
-1
votes
1answer
185 views

HMAC-Ripemd-160 in TrueCrypt

I'm wondering if it is still secure. I know TrueCrypt closed its doors but I continue using it because the cryptoaudit didn't find any huge bugs or security issues in TrueCrypt. But I have a bad ...
1
vote
1answer
601 views

Is there a kind of OS entropy pool on Windows systems? [closed]

I am wondering if Windows provides an equivalent of /dev/urandom from linux ? Or any kind of system entropy pool ?
0
votes
2answers
397 views

Practical Attack on RSA

Currently I am designing an RSA based application, and I am thinking of how long should the key be in order to be secure against attacks. I know that RSA 4096 bit key can be recovered using Sound ...
-1
votes
1answer
68 views

Hiding and Binding key in Groth-Sahai NIZK proof system

In context of Groth-Sahai NIZK proof system, I have a couple of doubts on Hiding and Binding keys. In case of hiding keys (highlighted in red), how is it ensured that $\tau(A) \subseteq \langle ...
-1
votes
1answer
104 views

Montgomery and Galois fields

I'm a little bit confused about the design of a RSA module in VHDL. My question isn't directly related to hardware design. I've read a lot of publications and I bought also a book. In one publications ...
0
votes
0answers
168 views

Two questions on EMSA-PKCS1-v1_5

If I implement EMSA-PKCS1-v1_5 in the following two non-standard ways, what kind of things could go wrong? The padding structure will be referred as (00|01|PS|00|DER(Digest Algo)|Digest), where | is ...
1
vote
3answers
809 views

RSA Key generation: How is multiplicative inverse computed?

As per Wikipedia, RSA keygen goes like this: Choose two distinct prime numbers p and q. Compute $n = pq$. Compute $\varphi(n) = (p − 1)(q − 1)$. Choose an integer e such that $1 < e < ...
2
votes
1answer
131 views

chacha20-poly1305 padding and length encoding

The AEAD construction for chacha20-poly1305 described in the IETF proposal encodes message lengths into the text that is to be hashed. The newer proposal goes further and pads associated data and ...
2
votes
1answer
75 views

Differential Privacy and appropriate noise distribution

In differential privacy solutions and more specifically for queries that they do entail counting the proposed solutions define the Laplace distribution that is best calibrated for low error. Other ...
2
votes
1answer
70 views

Feldman's VSSS: Showing the Correctness of shares that are Consistent

This is something with which I am struggling to get my head around. In Feldman's VSSS, I am aware that the Dealer broadcasts exponentials $a_{1},...,a_{t-1}$ of the secret $K$ and the coefficients ...
0
votes
1answer
137 views

Why should I use X.509 Authentication over PKC based Authentication?

So I have two examples and I don't understand why one would be chosen over the other. Example 1. A sends EPUb[r1] to B (asks B to prove knowledge of ...
4
votes
2answers
189 views

Why are some x-coordinates unsuitable for an ECDSA generator point?

For Bitcoin's ECDSA curve (secp256k1, where $a=0$, $b=7$), why can't the generator point's first coordinate be $x=0$? That is, the point on the curve would be $(0,y)$ where $y$ satisfies $y^2 = 0^3 + ...
3
votes
0answers
101 views

Performing HMAC with random key before MAC comparison

In Laravel (a PHP framework) I can see that they calculate a HMAC with a random key over the final HMAC before comparison. This additional HMAC calculation is of course performed for both the ...
2
votes
1answer
739 views

How to implement HMAC SHA-256

I am trying to figure out how the HMAC SHA-256 hashing algorithm works. I know that we have to use the following: H (K ^ opad)|| H ((K ^ ipad)|| text)). The ...
1
vote
1answer
67 views

Verifying identity using a sha-1 hash

I was reading http://blog.zorinaq.com/?e=74 which is about a Windows kernel developer. The developer proves that he is an actual developer by posting the SHA1 hash of a particular revision of a file. ...
2
votes
2answers
165 views

What if OT breaks in Yao's garbled circuit?

Two semi-honest parties are computing F with Yao's garbled circuit. Sender garbles it with his inputs baked in then sends it to the receiver. At this point the receiver must use OT to get his keys. ...
0
votes
2answers
129 views

RSA signing security

I'm curious about the security of RSA signing with the same public private key pair when the same message is sent multiple times. It's my understanding that once you generate the hash of the message ...
3
votes
0answers
65 views

Pollard's Rho - Restricting the random function to the exponents

Pollard's Rho is usually constructed using a function $f:G \rightarrow G$ which behaves 'random enough' in order to detect a collision with Floyd's cycle detection trick. It is easy enough to observe, ...
1
vote
0answers
86 views

Exploration of Blum Micali Security By Seed Size

I'm new to cryptography and am most intrigued by mathematically based pseudo random number generators. With reference to the Blum Micali algorithm: $X_{i+1} = G^{X_i} \bmod P$ can security be ...
-3
votes
1answer
138 views

I have a keyword and cipher text but cannot decode it please help! [closed]

coded text: ij gj hnev xudmyx hn igim umif obaxidyw kxzq si the key is JULIET, but i cannot figure out how it is used. Any help would be awesome!
0
votes
1answer
345 views

Help converting sha256 to 32-bit stream

I need some help with hash value calculation. I am a bit confused by this statement that I found on w3 website on calculation of a DigestValue for xmldsig ( ...
0
votes
0answers
107 views

Is ASCON cipher broken?

http://eprint.iacr.org/2015/030 present several attacks of ASCON but does not have a conclusion section. I'm having troubles estimating what are the consequences on the use of ASCON. What's your ...
1
vote
1answer
204 views

How does bitmessage encryption work?

I have been reading around protocol specification and there is either too much technical detail or too bad articles on various sites. I need you to explain in simple words how encryption in ...

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