0
votes
1answer
123 views

How many attempts does it take to crack a 32-bit password hash with this scenario?

How many attempts does it take to crack (match) a 32-bit password hash from a database of 4 million password hashes? Correct me if I'm wrong, but to crack a 32-bit password hash would take roughly ...
0
votes
0answers
41 views

Affine transformation in finite field SubBytes

Can anyone please explain how this computation was done? I picked it up from How are the AES S-Boxes calculated? The affine transformation is as follows. The input bits are multiplied against the ...
1
vote
2answers
138 views

Given infinite unencrypted and encrypted texts, can I find the algorithm?

Given an infinite amount of both unencrypted and the corresponding encrypted text, would I be able to calculate the algorithm? I am relative new to cryptography and don't know if I would be able to ...
0
votes
1answer
55 views

Is it necessary to encrypt nonce in cryptographic communication?

Server and client have a pre-shared key K. Assuming that that pre-shared key is safe, so nobody other than server/client can encrypt/decrypt. Client sends a nonce N to server, server then sends back ...
0
votes
1answer
133 views

What prime lengths are used for RSA?

Let's assume we have an RSA 2048 that was produced by two primes multiplication. What is the digit's difference in those 2 factors? For example one prime is 1024 digits and second one 1024 or, one is ...
1
vote
2answers
75 views

Equivalent key size between HMAC and AES?

I have seem comparison between AES and RSA, e.g., AES 128 bit key is equivalent to RSA modulus 3072 bits. Is there such comparison between AES key size and HMAC?
1
vote
0answers
109 views

ECC considered secure in OpenSSL?

this is my first question, please bear with me if it comes across silly. If I openssl ecparam -list_curves on my OpenSSL version (1.0.1f), it spits out the ...
0
votes
0answers
67 views

Pseudorandom number generators based on hard problems in mathematics

I know that Dual_EC_DRBG's security is based on the ellitpic curve discrete logarithm problem, Micali-Schnorr is based on the difficulty of factorization, and MQ_DRBG is based on multivariate ...
1
vote
1answer
52 views

How to store and use a Cryptographic Seed in a database [closed]

Companies such as Barclays use cryptographic seeds (for their PINsentry system), RSA do the same for RSA SecurID, but how do they safely secure the seeds in the database. With passwords you just hash ...
1
vote
1answer
69 views

Questions about updating the secret key of RSA?

I want to update the secret key of RSA. I understand there exists a common modular attack on RSA. Precisely, if adversary knows $(e_1, m^{e_1})$ and $(e_2, m^{e_2})$, where $e_1$ and $e_2$ are the ...
1
vote
1answer
49 views

Decryption of message in IBE without random oracle using bilinear pairig reg

I find the following IBE scheme from the videos posted and i don't understand the decryption algorithm, will any one please elaborate the 6th step scheme Setup($\lambda$) : $(\mathbb{G}, ...
0
votes
1answer
114 views

SHA-512 Length Field - What is it?

If I am using SHA-512 on a message and need to determine the padding field and length field, how do I determine the length field? I think I understand the padding, but not the length field. For ...
3
votes
2answers
147 views

Alternative sources of random numbers

Considering that algorithmic methods for generating unpredictable streams are hard to come by, I've wondered if any of these potential sources are good for making keys, seeds, and the like: stocks, ...
1
vote
1answer
47 views

How does the attacker include input before compression and encryption in CRIME?

I have read this article about the CRIME attack against TLS and SPDY. The article says that: What is not yet clear is how the attacker is including their input in the source material before it ...
0
votes
1answer
43 views

Requirement for the exponent generation during DH protocol [duplicate]

The setting is classic DH protocol. Alice computes $A = g^a \bmod p$. Alice then sends $A$ to Bob. Then Bob will send $B = g^b \bmod p$ to Alice. Are there any requirements for the values $a$ and ...
1
vote
1answer
64 views

Crypto++: How to re-generate pseurandom integers in Crypto++

I'm using Crypto++ to implement my protocol to mask a value $y_i$ by a seudorandom value $r_i$ such that $m_i=y_i \cdot r_i$. Since there are many $r_i$'s I want to generate them using PRG and then ...
1
vote
0answers
133 views

Evaluating Algebraic Complexity of a S-box

While studying the design and the desirable properties of an AES S-box , I came to know that Algebraic Complexity is also an important property of an S-box which is usually considered while evaluating ...
1
vote
1answer
53 views

Counter Mode (CTR) and mult-CPA

I am not sure if Counter Mode (CTR) encryption is mult-CPA (chosen-plaintext attack) secure or not.
1
vote
1answer
142 views

How to accurately calculate Unicity Distance for English?

The Unicity Distance for the DES cipher is around $8.6$ characters, and can be calculated using the $U=H(k)/D$ formula, where $D = R - r$, and where $R = 8$ is the number of bits in a byte (ASCII is 7 ...
1
vote
1answer
110 views

Factoring two RSA modulus with known $|p_1 - p_2| < \ell $

I have two 1024bit RSA modulus $N_1 = p_1q_1$ and $N_2 = p_2q_2$ such that $0 <|p_1 - p_2| < \ell$, and $\ell$ is at most 64bit integer. Can I factorise $N_1$ and $N_2$? What's the answer when ...
5
votes
2answers
207 views

Anonymous Gravatar Problem

Gravatar is a service that serves avatars for users based on md5(email_address). The hash is embedded on websites, so it's public. One of the problems with this ...
0
votes
1answer
54 views

Hashing - Digital Signing and Trivial Stretching

Two very basic questions: 1. Digital Signing Why is it not possible to just simply replace the hash value from the request? Examples: ...
0
votes
1answer
146 views

Symmetric mutual authentication with client using a derived secret

I'm attempting to find a client/server authentication protocol that allows the client and server to authenticate each other when the client doesn't know the server secret but does have a sensitive key ...
2
votes
2answers
140 views

Which characters to take into account when calculating unicity distance?

I need to calculate the unicity distance of a block cipher. Assuming I know that the plaintext is an English message I considered using 53 as the size of the alphabet, since the message could contain ...
1
vote
2answers
77 views

Explanation of each of the parameters used in ECC

I'm having a very difficult time finding a clear explanation of the parameters used elliptic curve cryptography. I know for certain that $p$ is the number or order or whatever of the given field that ...
0
votes
1answer
90 views

Java RSA Padding: no libraries used

I'm trying to implement RSA without using any java libraries using the algorithm from wikipedia HERE So, anyone can clearly see that it is a raw RSA, and can directly be attacked. The question is ...
0
votes
2answers
111 views
0
votes
1answer
52 views

Text in random image encoder: is it flawed?

I have created a small cryptographic programme: You input your text A random image is generated Random coordinate pairs in number equal to the chars of the message are generated. The red component ...
0
votes
2answers
83 views

General questions about cryptography for password security

I'm pretty new to this and find it quite interesting, but my brain won't process how it works so I have to ask some questions :) Why is cryptography used? Is it for extra security once the password ...
2
votes
1answer
62 views

How to construct the blind factors in practice?

I'm Implementing a protocol that uses masking techniques (or blinding factors), so we can mask a value $y_0$ as $m_0=y_0 \cdot r_0$ where $y_0 \in \mathbb{Z}_p$ and $r_0 \stackrel {R}\leftarrow ...
2
votes
2answers
76 views

Does key derivation with known parameters add any security?

First up: this is a question about a concept that I try to wrap my head around; it is not about the specific implementation. Anyway… I have the following scenario (simplified to show the problem I ...
1
vote
2answers
63 views

If Blum Blum Shub is modified to use a prime modulus, is it still secure?

The definition of the Blum Blum Shub cryptographically secure pseudorandom number generator is $x=x^2 \mod N$ where $N=p \times q$, $p \in \mathbb P$, and $q \in \mathbb P$. Supposedly, the security ...
-1
votes
2answers
87 views

Is the complexity of Caesar (shift) ciphers “n * n!”?

Can we say that any shift cipher to be decrypted needs an algorithm of complexity “n * n!”? (where n is number of possible ...
1
vote
1answer
58 views

Pseudorandom function library [closed]

I'm wondering if there is any library supporting pseudo-random function, so I can specify the key length and output domain. Is it correct that I need to use a block cipher for this purpose? Any ...
0
votes
2answers
78 views

Why not just encrypt the message and the hash of the message to achieve cryptographic integrity? [duplicate]

I've always seen MACs as a way to provide integrity and authentication. You would just append it to some message in clear. But this is clearly not the case when you're doing Encrypt Then Mac. When ...
0
votes
1answer
57 views

Check if this cryptosystem is safe

Let $G$ be any group where group operations, as well as finding the inverse of an element, can be performed quickly, but the discrete log problem is difficult. Consider the following cryptosystem: ...
0
votes
1answer
40 views

Is the key deducible with AES CTR when we know about the plaintext, IV and the ciphertext? [duplicate]

Simply as stated, with AES running in CTR mode, can somebody work out the key (without brute-forcing) given we know about the plaintext, IV and also the ciphertext. Assuming we also know about the ...
0
votes
0answers
14 views

Can a tree hash with leaf-size of 1 byte support verification of content with elided ranges, at a cost of at most 2 supplied internal-node hashes?

Perhaps someone can confirm my intuition: A tree hash with leaves of size 1 (for example Blake2 in a tree-hash mode) would of course not be very efficient. But it seems that it might be a suitable ...
1
vote
1answer
60 views

3DES Modes EED orEDE?

Can we use EED with 2 keys (K1 K1 K3) rather than EDE (k1,k2,k1) ? We measure the strength of DES by the effort (in term of number of tries) in finding some K1 & K2 to match a known plaintext and ...
-3
votes
1answer
113 views

Attacking multi block MAC constructions

For variable-length messages, there are three different ways to generate the tags. $Tag = MAC_k(\Sigma_i m_i)$. $t_i = MAC_k(m_i)$ and $Tag = (t_1, ..., t_l)$. $t_i = MAC_k(i||m_i)$ ...
0
votes
0answers
52 views

Strategies for securing public key storage on software

I´m kind of new in this so I apologize in advance for any noob mistakes (feel free to point it out) We are developing a licensing mechanism on our software, and I would like some advice. The ...
1
vote
1answer
73 views

Generic name for (?hash) functions of form $\{0,1\}^n \rightarrow \{0,1\}^{poly(n)}$

Consider a function $$f: \{0,1\}^n \rightarrow \{0,1\}^{poly(n)} $$ with the following properties: hard to invert, i.e. given $f(x)$, hard to find $x$ hard to find a collision, i.e given $f(x)$, ...
0
votes
0answers
58 views

Deriving a decryption equation

Consider a very simple symmetric block encryption algorithm, in which 32-bits blocks of plaintext are encrypted using a 64-bit key. Encryption is defined as C = (P⊕KL)⊗KR where C = ciphertext; K = ...
0
votes
1answer
33 views

FIPS-Compliant SHA2

I want to use SHA-512 for hashing in a system that must be FIPS-compliant. When I look at the FIPS 140 list of approved providers, I don't see SHA from any provider as being an approved algorithm, I ...
1
vote
1answer
115 views

Diffie-Hellman Application

Alice and Bob want to perform a Diffie-Hellman key exchange using the group $G$, a primitive root $g$, Alice’s secret key $k_A$ and Bob’s secret key $k_B$. In each case below compute the element of ...
0
votes
1answer
70 views

Is the idea of a known plaintext attack really that new?

As you can probably guess, I just watched The Imitation Game, which hasn't really gotten points for historical accuracy... During World War II, Turing and his team fret that they can't know the ...
0
votes
1answer
66 views

Prime modulus for RSA and sharing a secret?

According to this paper entitled "Using Commutative Encryption to Share a Secret" they define their modulus to be a large prime p, which is public. Both exponents are private in this case. According ...
0
votes
1answer
62 views

Self changeable key [closed]

If key changes itself when it send/receive message what would be could breaking method? So: $E: m×k$ in which $k$ is last generated key $D: c×k$ in which $k$ is last generated key $k{_n} = ...
1
vote
2answers
98 views

Why does NaCL have different keys for signing and encryption?

I want to start using NaCL to sign messages that will go into a message queue, and I noticed that it generates different keys for each operation. Is there a reason for this? Can I not use the same PK ...
0
votes
0answers
42 views

Key establishment protocols other than Diffie-Hellman

Are there any key agreement/exchange/establishment protocols which are NOT based around the Diffie-Hellman protocol or handshakes using public key cryptograaphy? DH seems to form the basis of this ...

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