0
votes
1answer
11 views

Length of prime number used in Pedersen Commitment

I am writing a program using a Pedersen commitment and all I'm missing is an appropriate length for my prime p. I have heard that a length of 2^80 is ok, is that correct?
2
votes
0answers
18 views

Proving that a plaintext is the Paillier decryption of a certain ciphertext

Assume that Alice received 100 ciphertexts encrypted with additive homomorphic encryption, say Paillier, using the same public key that belongs to Bob. Alice added all of them, and wants to know the ...
-2
votes
0answers
21 views

How can I understand Shamir's attack on Merkle-Hellman Cryptography?

How can I understand Shamir's attack on Merkle-Hellman Cryptography? Please, explain it in layman's terms.
0
votes
1answer
10 views

Using HMAC SHA256 to protect payment files in local trusted network

in a project that I am working on we have been tasked with eliminating PGP while providing sufficient security to protect payment files only within the Company's trusted network. We arrived at HMAC ...
2
votes
1answer
13 views

Is MCrypt's 8-bit OFB mode secure?

I just stumbled across a Stack Overflow post which points out that the libmcrypt library (notably used in PHP) implements a somewhat unusual set of block cipher modes: it calls the usual CFB and OFB ...
0
votes
1answer
27 views

Retrieve value of private key after encryption with the public key

Is there a way to find an RSA private key after it is encrypted with the corresponding public key? Does there exist an algorithm to recover the private key in this special case?
3
votes
1answer
134 views

Why does applying 56-bit DES twice only give 57 bits of security?

Given two 56-bit keys, $k_1$ and $k_2$, why does $E_{k_1}(E_{k_2}(M))$ only give 57 bits of security? So basically I'm unsure why it only gives 57 bits of security; I understand that one key will ...
-2
votes
0answers
32 views

Need urgent help solving a riddle [on hold]

We got this riddle during a contest. This code requires 36 characters to be used: a->z AND 0->9. Can you solve it? hacgp6by68astytga5azagndca8jopc Need help solving it.
0
votes
0answers
27 views

What are the links between Cryptography and Algebraic Topology?

I have asked "What are application of Cryptography in Algebraic Topology". But I want to know whether are there any relation between Algebraic Topology and Cryptography. Are there any application of ...
-2
votes
0answers
18 views

Unlock my ZipCrypto deflate [on hold]

Can anyone help me I have forgot my password for my file.. ZipCrypto deflate. I need a software to unlock the file. Please anyone assist me on this matter
-2
votes
0answers
16 views

suitable method for encryption and decryption

I want to encrypt and store important data in mysql so that no one else can access its original form and I want to decrypt those data whenever required. Which encryption scheme is suitable for this ...
0
votes
1answer
21 views

Combining cascaded encryption keys into one key

Is there an encryption algorithm where it's possible to combine multiple encryption keys into one, so that: $E_{AB}(Data) = E_A(E_B(Data))$ KeyAB should be computable from KeyA and KeyB, but it must ...
0
votes
1answer
46 views

Knowing N and a relationship between the 2 prime numbers(p and q) find p and q generated with RSA

Let there be $p$ and $q$, 2 prime numbers for which the following relationship is true: $|p-q| < 2 \cdot N^{1/4}$. The algorithm first generates the prime number $p$, then it generates $q$ close ...
0
votes
0answers
41 views

What are application of Cryptography in Algebraic Topology [on hold]

What are application of Cryptography in Algebraic Topology, specially in Category theory?
0
votes
1answer
32 views

What type of encryption is this? [on hold]

I need to know what type of encrpytion is this, ed6467d63c907d220447b00bf875e4e017702ff5
0
votes
1answer
40 views

Integrity compromised - HASH modified

As we are all aware that HASHing is user to verify integrity in cryptography. I have a query about hashing. Suppose a man in the middle attacker manipulates the data and creates new HASH (by running ...
0
votes
0answers
37 views

encryption key ends with same pattern [on hold]

We have used "AES algorithm".key length is 256 bit.It is using same secret key to generate multiple encryption key.ALL encryption key ends with same pattern.What is the reason for this.transformation ...
1
vote
1answer
37 views

Is authentication length always a subset of encryption length?

Do in all the use cases, if I have to encrypt and authenticate, encrypt-then-authenticate or authenticate-then-encrypt, like in IPSEC, SSL or SSH or others, if I were to do these operations to a ...
1
vote
1answer
45 views

Vigenère, auto-correlation vs Kasiski examination

What are the differences between 'Kasiski examination' and 'auto-correlation' ? In Cryptool site, they state that autocorrelation analysis is more efficient and clearer than the Friedman or Kasiski ...
2
votes
2answers
57 views

Key space vs Cardinality of 1024-bit RSA

I have been trying to figure out the encryption key space, and cardinality of 1024-bit RSA. From my understanding, the key generated from 1024-bit will be primes greater than $2^{1023}$ but less than ...
0
votes
1answer
42 views

Are keys generated by the user or block cipher algorithms themselves? [on hold]

We know block cipher algorithms. In the block cipher algorithms, Key Scheduling is the one crucial part. I see that in some simulation programs of the AES,DES,TripleDES encryption algorithms. In ...
0
votes
1answer
46 views

Finding Vignere Cipher key

I am new to cryptography and I am just trying to find key for random text. Can please explain the easy way how we can find the key in small number of steps ? if we have text like Peit Wokm! Mhfa ...
0
votes
0answers
41 views

Why is the call to RSA_generate_key_ex() failing sometimes? [on hold]

I'm trying to randomly generate a pair of RSA asymmetric keys, however with my current implementation, the RSA_generate_key_ex() method seems to hang forever. I'm unable to extract an error code ...
0
votes
1answer
39 views

How do I control an access code safely?

Upon registration an user has to specify an access code of five digits. This access code is also used as a password for the encryption and decryption of certain strings. The user types in "12345" ...
3
votes
1answer
46 views

dh parameters someone else generated

Am am auditing some software that includes compiled in DH parameters (2048 bits). I can't be sure who generated the DH parameters or how they were generated. Question: Can DH parameters be weak ...
0
votes
0answers
18 views

Does it make sense to have multiple values of authentication and cipher offsets while encrypting a packet?

Consider a packet with N segments. cofsset(cipher offset - from where one must cipher) lies in arbitrary Segment "A". aoffset (authentication offset - from where one must authenticate) lies in ...
0
votes
1answer
42 views

RSA modulus (N) from public key and calculating N from p, q not equal [on hold]

I have a RSA public key in the form of public exponent and modulus as follows: ...
0
votes
0answers
18 views

EC based password authenticated key exchange protocol

I would like to know: What is the currently best (efficiency and security wise) known EC based password authenticated key exchange protocol? (i.e. is there any EC based protocol may be similar to DH ...
0
votes
1answer
26 views

nonce of AES-GCM in SSL

It seems that the nonce of AES-GCM in SSL has 3 parts: salt, 4 bytes, generated in handshake, not changed in whole session nonce_explicit, 8 bytes, chosen by the sender and carried in each SSL ...
0
votes
1answer
30 views

Why perfect secrecy can be ensured when a plain message and a cipher-text based on one-time pad are correlated?

First, some well-known results are as follows. For random variables $X$ and $Y$, we have $$H(X,Y) \leq H(X) + H(Y).$$ The equality is achieved when $X$ and $Y$ are independent. Second, in one-time ...
0
votes
2answers
45 views

Fortuna: why are source ID and data length added together with entropy data into the pools

Section 9.5.6 of Cryptography Engineering states that The concatenation [of source number, length of data, and data itself] is then appended to the pool. Why are we including source number and ...
0
votes
0answers
15 views

Website Certificate with different public key [migrated]

I've installed a ssl certificate from https://www.startssl.com/ in a server running with plesk. The website is the following: https://refood.sal-pimenta.pt/ As you can see the certificate is fine but ...
0
votes
1answer
28 views

what is legend of h(r) in this protocol?

can you help me what is legend of h(r) in below protocol? ‎‎$A‎\leftarrow‎{B}\quad:{h(r)‎‎}{,B}{,P{_A(r,B)}}‎\\A‎\rightarrow‎{B}\quad:r$
-1
votes
0answers
51 views

can you attack to this protocol? [on hold]

can you attack to this protocol? ‎$ ‎A‎\rightarrow{B}‎‎\quad:\ P{_B(r_1,A)}‎\\A‎\leftarrow‎{B}\quad:\ P{_A(r_1,r_2)}\\A‎\rightarrow‎{B}\quad:\ r_2‎$ ‎$P_A,P_B\ are\ public\ keys\ and\ r_1,r_2\ are\ ...
5
votes
0answers
52 views

Factoring two RSA moduli $N_i=p_i\cdot q_i$ knowing that $p_2=p_1+2$?

It is given two RSA moduli $N_1$ and $N_2$, known to be of the form $N_i=p_i\cdot q_i$, with $p_i$ and $q_i$ unknown primes, and such that $p_2=p_1+2$. Can we make use of that relation to factor the ...
-1
votes
0answers
31 views

nonce is a number that use once.so why in many protocol use nonce several times?

the Nonce is "a number that use once".so why in many protocol use nonce several times? how use nonce in protocols? if problem is save of nonce in database,how saved time stamp and signature in ...
1
vote
0answers
21 views

Difference between IPSEC SA and CHILD SA [migrated]

Let us consider two network entities. ...
0
votes
0answers
49 views

Popularity of ECMQV authenticated key agreement protocol

I've got a few ECMQV related questions: Why is ECMQV a more efficient EC-based authenticated key agreement protocol? Why is ECMQV so popular? Is it because no other protocol of its strength exists? ...
-3
votes
0answers
50 views

Is there any method to avoid the differential cryptanalysis? [on hold]

May I know the Best ways to avoid the Differential Attack in block cipher algorithms (AES,Speck,Simon etc). The probability of differential cryptanalysis is achieved mostly equal to 1 in speck light ...
-1
votes
1answer
33 views

What does L_n is the bit length of the group order n states need for my calculation in ECDSA algorithm?

I am doing the program of implementing ECDSA for which I am trying to solve the equation scenario. In ECDSA that signature generation algorithm which states as hash value from the SHA-1 and where $l$ ...
0
votes
2answers
112 views

Asymmetric encryption that is secure for (almost) any foreseeable future

Recently, I've been reading a couple of papers about building cryptosystems that are secure for up to 30 years. But for some applications, this seems a bit low to me. So I am wondering if considering ...
1
vote
0answers
103 views

Is chaotic encryption secure?

I know this sounds too broad. But I noticed that there was a chapter on chaotic crypto in the recent Handbook of Information and Communication Security Editors: Stavroulakis, Peter, Stamp, Mark (Eds.) ...
4
votes
3answers
87 views

Is there a way to use bcrypt with passwords longer than 72 bytes securely?

From my understanding BCrypt truncates the password to 72 bytes. If a password is longer than 72 bytes, what is a way to store that password using bcrypt securely without compromising it? Or is this ...
0
votes
1answer
63 views

Inserting a backdoor into a cryptographic hash function

I'm curious as to how a backdoor can be built into a hash function. What might it take the form of? What's probability of getting one that can be backdoored in a way that can actually undermine its ...
5
votes
2answers
74 views

What is a Key Derivation Function?

From Wikipedia: In cryptography, a key derivation function (or KDF) derives one or more secret keys from a secret value such as a master key or other known information such as a password or ...
2
votes
0answers
30 views

Encrypt-Mix-Encrypt: Full Diffusion?

I've read this paper about the encrypt-mix-encrypt mode for ciphers and was asking myself if this mode provides "full" diffusion. So if an attacker alters one bit of the ciphertext, how many bits ...
0
votes
0answers
40 views

why are both ipad and opad required for HMAC?

I was reading about HMAC and why it is crucial to avoid security issues with normal prepending / appending the secret k to a message (issues due to merkel damagard construction). I am not familiar ...
1
vote
1answer
38 views

Are there equivalent IVs in DES/CBC?

I'm playing around with the CryptoPP library with DES/CBC and I've noticed that for some sets of data, if I decrypt the ciphertext with Key1, IV1, I get a good cleartext result -- but if I decrypt the ...
0
votes
1answer
54 views

Choosing finite field size in Shamir's Secret Sharing Scheme

The Wikipedia article on Shamir's Secret Sharing says to that to have information theoretical security the splitting algorithm should be evaluated using finite field arithmetic on the field ...
3
votes
1answer
253 views

Weaker alternative to Ed25519?

For me, the main advantages of Ed25519 are that it avoids patents (by computing in one dimension) and that it is fast. However, the 128bit security of Ed25519 is sometimes too strong to comply with ...

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