All Questions

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1answer
182 views

What does the cipher-text overhead means?

I have two questions here. What does the cipher-text overhead means? Why we were suggested not to encrypts the plain-text itself instead just encrypts only the key (i.e random number)
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1answer
83 views

What kind of adversary is a compromised party?

Imagine multiple parties executing a secure multiparty computation protocol to evaluate a function securely. Let Alice be one of the parties who is intended to get all the partial results and combine ...
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2answers
240 views

Recommended authenticated stream cipher for minimum overhead?

I'm running my TCP/IP protocol secured by encrypting each packet with AES128/CBC, bundling a SHA256 HMAC over that packet. This causes quite a bit of space overhead for small packets, so at first I ...
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2answers
140 views

The security of the AES secret itself

I am writing an application, running on a server, where multiple users access data from a database which is AES encrypted with a master secret. The master secret itself is initially randomly ...
0
votes
1answer
111 views

what actually the function for e(g,g)^xy

I doing a project using ABE "Attribute-Based-Encryption" but i didn't understand what actually the function for $e(g,g)^xy$. Just tell what's the calculation need to perform here. I gone through no of ...
0
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1answer
136 views

What key length is required to keep simple keyed “hash” secure?

In a previous question, I described a particular keyed "hash" that mapped a 5-digit input code into a 5-digit output code. It used a 8-bit key which is very insecure - more than 99% of the time, you ...
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votes
2answers
145 views

Physical Level Encryption

What types of algorithms that are capable of signing a message are out there that run on a physical level, e.g. lacking the infrastructure of a standard PC, no memory, processor or motherboard in the ...
0
votes
1answer
76 views

How to hash a structure that needs to include that hash's outcome?

so I am busy writing a TCP protocol in which I send a "packet header" with each packet of data. This packet header is a structure that contains information about the data that was sent. I want to ...
0
votes
1answer
125 views

Certificate == signed public key

For primes p and q used to create a keypair, I understand that the following operation is used to create a signature: $M^d (\bmod\ N)$ where d and N have their usual meanings and M is the message. ...
0
votes
1answer
430 views

Ciphertext-only attack on Simplified DES

Is it possible to deduce the plaintext block or the key, given only a Simplified-DES ciphertext block (e.g. c=01110110)? I'm reading Cryptography And Network Security, by William Stallings and I'm bit ...
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2answers
88 views

Voice Call Safety [closed]

When i was dealing with an assistant of my bank through mobile call, she asked me to insert my bank login code after a beep. I was wondering if this procedure is secure against a Man In the Middle ...
0
votes
1answer
141 views

Can one detect if two pairs of elements in Zp have the same exponential relation?

Suppose that $p$ is a safe prime of 2048 bits ($p = 2q + 1$, and $q$ is prime). Suppose that one is given two pairs $(x_1, y_1)$ and $(x_2, y_2)$ such that: $y_1 = x_1^{r_1} \pmod p$ $y_2 = ...
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votes
1answer
1k views

GPG vs PGP vs OpenSSH and management of them [closed]

What is the main difference of the three? Can I use only one of them for everything (e.g. GPG for SSH authentication) If I encrypt my private key with a pass-phrase, is it strong enough so that if ...
0
votes
1answer
123 views

Secure way to compare two secret numbers without disclosing them?

For example, two people want to know who is the older, without disclosing their age. Is there a secure way to do this without a third party involved?
0
votes
1answer
197 views

Is there a problem with constructing a CSPRNG using MD5 or SHA1?

Is there any security concerns with building a CSPRNG using a broken hash function like MD5 or SHA1? The design is such that a CRC-like function is used for mixing entropy and MD5 is used as the ...
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2answers
323 views

Cryptographic Symmetric Stream Cipher

Let me know a cryptographic symmetric stream cipher system with only two functions say S() and P() and it should satisfy the ...
0
votes
1answer
495 views

detecting ROT13/base64 encryption

Is there anyway to detect that a cipher is encrypted with ROT13 Or Base64 without decrypting it using the algorithm and check that the result means (works)? I mean does an algorithm exists that test ...
0
votes
2answers
377 views

Does gpg's symmetric encryption keep information about the filename?

If I encrypt a file with gpg -c file.zip, and change the filename. Is there any way I can restore the filename as I used as a password. or the name encrypted to?
0
votes
1answer
329 views

Matrix Multiplication of Bits

How to multiply the matrix of bits example I have two 4x4 matrices of bits ...
0
votes
1answer
625 views

How to implement order preserving encryption or order preserving hashing [closed]

Does anybody know any free implementation of either order preserving encryption or order preserving hashing? I've found some codes like CMPH but I need to dynamically add new DATA and that's why most ...
0
votes
1answer
85 views

inverse of 985 mod(φ60131)

Alright Ive been working on this one for a while I found φ(60131) to be 97294 ½(60131+60131(5)^.5) = 97294 then I worked through the GCD ...
0
votes
1answer
2k views

Is MAC better than digital signature?

MACs differ from digital signatures in the sense that MAC values are both generated and verified using a shares secret key. Does this in any way put MAC on a disadvantage as compared to digital ...
0
votes
1answer
21 views

Direct sum of Binary numbers In Mixcolumns

I have just started learning cryptography and I am trying to make sense of the direct sum on some binary numbers. I am trying to find a column of a state space after a Mixcolumns operation has been ...
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2answers
58 views

public key certificate on TLS/SSL

Currently I am working on a public key certificate. I got a question: Why is a public key certificate needed for TLS/SSL? Wouldn't TLS/SSL itself is enough? What is the role of the certificate?
0
votes
1answer
72 views

RSA CRT modulo reduction

I am working on RSA CRT and there is a point that I don't understand : So we have $n=pq$ and $c = m^e \bmod n$ an encrypted message. To decrypt $c$ with RSA CRT, we have to compute : $d_p = d \bmod ...
0
votes
1answer
93 views

Is there any probabilistic version of RSA?

I have now studying the RSA, but I think that is it possible to have some probabilistic version like a random bit string "r" XORed with the key? Is there any probabilistic version of RSA? Thak you ...
0
votes
1answer
52 views

Encrypt a file for random access but only after an initial read of the whole file

I'm symmetrically encrypting a file (using a random salt and a user supplied password with PKCS5S2, i.e., nothing special) and I need to be able to access it randomly. Therefore I'm using a stream ...
0
votes
1answer
35 views

MD5 update functions

In the hashlib module in python is a function called m.update() where m is a ...
0
votes
1answer
37 views

blowfish ecb with openssl doesn't give the expected result

I do the following via the Linux CLI: ...
0
votes
1answer
40 views

HMAC_DRBG Generate Process: requesting N bytes at once different from requesting N bytes in total?

Am I correct in assuming that HMAC_DRBG would return different results if I, e.g. first request 4 bytes followed by a request of another 4 bytes instead of asking for 8 bytes at once? It seems that ...
0
votes
2answers
83 views

Database row level encryption scheme

I am wanting to secure some highly sensitive data in a database. This would mean that the data needs to be encrypted and remain secure for 100 years if it were to fall into adversary hands. I also ...
0
votes
2answers
63 views

I'm using AES-CTR as a CSPRNG - Do I need an IV?

I'm using AES128-CTR for generating pseudo-random values, which is considered secure for up to 1MB (at least from what I've read). I simply encrypt a 128-bit little-endian counter, starting from 0. ...
0
votes
1answer
101 views

How does Blowfish avoid successful cryptanalysis? [closed]

I have researched the Blowfish algorithm and am curious as to why there exists no effective cryptanalysis for this algorithm as of yet. What basic principles or features allow Blowfish to achieve ...
0
votes
1answer
72 views

A variant of Shamir secret sharing

Suppose implement the Shamir secret sharing as following: we select a degree $d$ polynomial $P$ with a zero coefficient of 0, and all other coefficents selected randomly from $Z_p$; and to this ...
0
votes
1answer
62 views

Known-plaintext attack on two-dimensional affine cipher

Problem: We have a two-dimensional affine cipher with $n = 2,\,\,\,\mathcal{P} = \mathcal{C} = {\mathbb{F}_{16}^2}$, where $\mathcal{K} = \{ A,\,\,b\} $ and $b = (0,0)$. The encryption and decryption ...
0
votes
2answers
58 views

Brute Force Attack Strategies

A Brute Force Attack obviously involves attempting to decrypt ciphertext (with the associated plaintext being known) using all possible encryption keys. Aside from attempting all possible ...
0
votes
1answer
74 views

what is the difference between IBE and ABE schemes

Can somebody explain in simple words. real life example light help and limitations of these schemes etc.
0
votes
1answer
71 views

Is it possible to find out whether a number is greater than another number without knowing the numbers?

Is it possible to construct a zero knowledge proof that one encrypted number is larger (or not) than another encrypted number without releasing the values of either numbers?
0
votes
2answers
144 views

Why would an RSA library tell me that the public key must be at least 512 bits in size?

I'm trying to interoperate with a web service by reverse-engineering it. Currently, when sending a POST request, it encrypts the form data one-by-one with a 'RSA' function. But it's rather weird as ...
0
votes
1answer
64 views

How to calculate kinv from the given k value

I am implementing an ECDSA NIST test vectors verification application. The test vectors are taken from http://csrc.nist.gov/groups/STM/cavp/#09. One of the test vectors is given below: ...
0
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2answers
73 views

Does NTRU provide Perfect Forward Secrecy?

Does NTRU provide Perfect Forward Secrecy if the world would use it in an HTTPS connection?
0
votes
1answer
53 views

How can one generate pairs/triplets/…/n-ary MD5 collisions

Is there a way to generate n strings with the same MD5 hash?
0
votes
1answer
74 views

DES cipher breaking bruteforce method

I was reading upon Biham and shamir's paper and a fact has been presented over there - if $ P1 = \overline P2$ and I choose a key $K1 = \overline K2$ then in that case $$T1 = DES(P1, K1)$$ $$T2 = ...
0
votes
1answer
32 views

FSB Hash Functions and Convetional hash Functions

I'm reading FSB cryptographic hash function and the authors say that security of this function depends on NP-Complete Problem: "Decoding Linear Code Unlike most other cryptographic hash functions in ...
0
votes
2answers
129 views

Homomorphic Encryption: how does the equality test on ciphertexts work?

Let's suppose we have a asymmetric crypto-system $H$ which is homomorphic with respect to some function $F$. Alice encrypts a message $m$ with her private key $e$ in the crypto-system $H$ and ...
0
votes
1answer
192 views

Encryption and HMAC key derivation

I'm deriving keys from a user-supplied passphrase for symmetric encryption using AES-256 in CBC mode with a HMAC for authenticity/integrity. My key derivation function currently looks like this: ...
0
votes
1answer
106 views

One-time pad, zero key and Shannon

I'm supposed to prove that OTP without the zero key $k=0^n$ is not perfectly secret anymore. I understand that it's not because an attacker learns something by looking at the plaintext and ciphertext. ...
0
votes
1answer
134 views

Is this EdDSA modification secure?

I am hoping to employ a signed set membership system which is valid iff each signer's contribution to the set is present. The system should allow for two or more mutually exclusive signed sets to be ...
0
votes
1answer
87 views

RSA Proof - Is Z(n) closed under multiplication

In RSA proof it can be proved that $\mathbb{Z}^*_n$ is closed under multiplication. Can it be also proved that $\mathbb{Z}_n$ is closed under multiplication? If yes, then how?
0
votes
1answer
55 views

What cryptographic paradigm is appropriate for this use case?

This is a very newbie question... I have to quickly implement a solution for our application that works like this... We have a binary executable that is given a configuration file. I need to encrypt ...

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