0
votes
1answer
110 views

How can we prove that two discrete logarithms are equal?

Suppose there are two elements $a = g^x$ and $b = h^x$, where $g$ and $h$ are generators in $Z^*_p$ and $p$ is a large prime. How can we prove that $a$ and $b$ have the same discrete logarithms with ...
0
votes
1answer
102 views

IV = Filename XOR CipherKey?

i want to encrypt transparently using Rijndael. So this is, what I thought of and I would like to have an opinion from "Experts" whether this will harm encryption strenght. I am using chunks of 1MB ...
0
votes
1answer
133 views

Thoughts on secure hashing and the “mds” algorithm

Almost a decade ago Raymond Chen blogged [1] about the "hash reset attack" cautioning developers to record the content length in addition to the message digest. Recently I came up with a variation on ...
0
votes
1answer
400 views

Decrypt AES-128 with key file but missing IV? [duplicate]

I want to decrypt a file that has been encrypted using AES-128 in CBC mode using OpenSSL. I got the “.key” file – which is 32 digits – but when I try to decrypt with OpenSSL, the program asks me for ...
0
votes
1answer
116 views

HKDF vs TLS PRF. Which of the one is better? [closed]

Which of the one (HKDF or TLS1.1+ PRF) is more secure and why?
0
votes
1answer
126 views

AES CBC MAC splicing attack

I'm trying to implement AES CBC MAC splicing attack in Python, the idea is: given a message M, its tag Tm (MAC(M) = T), a new message N and its tag Tn we build a message such as: M||N = (M1, ..., Mn, ...
0
votes
1answer
2k views

AES Algorithm processing time in Arduino vs Raspberry Pi

The Arduino employs an 8-bit ATmega series microcontroller whereas the Raspberry Pi is based around a 32-bit ARM processor, and the Arduino is typically clocked at between 8-16MHz and with 2-8kB of ...
0
votes
1answer
535 views

ECC key size and signature size

My understanding of ECDSA signature length is that it depends on the key size. So for instance, if a "prime256v1" is used, the signature length will be 64 because (n/8)*2 and for "secp384r1" it will ...
0
votes
2answers
236 views

Convert a number to sha-1

I have a task to find a the message for which the SHA-1 hash's last 11 symbols in hexadecimal presentation corresponds to an 11-digit number. I have been given the following example solution: For ...
0
votes
1answer
98 views

Explicit Key SHA-1

I'm reading “Collision-Resistant Hashing? Towards Making UOWHFs Practical” and in the Section 2 it says: Hash functions like MD5 or SHA-1 have no explicit key. But no notion of ...
0
votes
1answer
368 views

Diffie-Hellman Secret Exponent Size and Shared Secret Usage [closed]

I'm developing my own protocol and I'll use Diffie-Hellman to achieve PFS. It will work in this way: The symmetric encryption algorithm will be AES_256_CBC. The DH parameters will be: P: a 2048-bit ...
0
votes
2answers
668 views

If I have the unencrypted text and the encrypted text, can I calculate the key?

If I have the unencrypted text and the encrypted text, can I calculate the key? It seems logical based on my limited knowledge of encryption that I should be able to... but it also seems like too ...
0
votes
2answers
115 views

The weak link is the password?

Consider a secure modern block cipher like AES/Serpent/Twofish. I hear everyone say that the complexity is $2^{128}$ for a 128 block cipher. But isn't the weak link the actual hashed and salted ...
0
votes
1answer
811 views

Implementing OpenSSL padding

I'm conducting an experiment dealing with differences in padding across different aes operations for my Intro to Crypto class, and the question says OpenSSL uses PKCS5 padding, and that I need to ...
0
votes
1answer
412 views

probability of N hash digits colliding

What is the probability of the first N hash digits colliding? for example i made a script that appends the first 5 digits of the file's sha1 hash to the name of the file. So will the probability of ...
0
votes
1answer
106 views

Distributed Asymmetric Key Decryption with threshold

Threshold decryption of public key encryption schemes allows the decryption key to be distributed among trustees. Then, to decrypt the cipher text it requires at least threshold t trustees to run the ...
0
votes
1answer
181 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)
0
votes
1answer
82 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 ...
0
votes
2answers
237 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 ...
0
votes
2answers
139 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
110 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
votes
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 ...
0
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
124 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
426 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 ...
0
votes
2answers
85 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 = ...
0
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
122 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
196 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 ...
0
votes
2answers
322 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
485 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
372 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
328 views

Matrix Multiplication of Bits

How to multiply the matrix of bits example I have two 4x4 matrices of bits ...
0
votes
1answer
612 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
39 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
30 views

MD5 update functions

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

blowfish ecb with openssl doesn't give the expected result

I do the following via the Linux CLI: ...
0
votes
1answer
34 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
78 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
61 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
97 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
60 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
55 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
69 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
69 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?

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