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Questions tagged [attack]

A cryptographic attack tries to theoretically and/or practically attack the security properties of a cipher and/or algorithm.

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Hash Collision Probabilities

Please give help! how can I calculate the probability of collision? I need a mathematical equation for my studying. Assume, I am using SHA256 to hash 100-bits. Thus: SHA256 {100} = 256-bits (hash ...
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1answer
64 views

ECDSA with common nounce?

I'm new to cryptography, and I've searching about ECDSA because I'm trying to solve a CTF. I've already check this site and Google, and I think I'm in the right path, but probably I am missing ...
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How to choose between password derivation or encryption? [migrated]

Suppose you use a password manager having all possible features of modern password managers: encryption with a key derived from your master password, auto-filling, cloud or local storage, browser ...
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42 views

Is there any MAC that satisfies UF-CMA but not UF-CMVA?

I need to find a simple MAC that satisfies UF-CMA but not UF-CMVA. A case in which Vrfy allows an Adversary to break the scheme.
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Is it possible to find the key for AES ECB if I have a list of plaintext and corresponding ciphertext?

Assume I have a list of plaintext text and its corresponding ciphertext which was created using a specific key with AES in ECB mode. Can I recover that key? If, how big does the list of plaintext ...
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1answer
91 views

Recovering plaintext from AES-128 given round key 10 and ciphertext

I'm working on an old CTF challenge where AES-128 was used on a 16 byte block. I have the round 10 key and the ciphertext. What techniques exist for obtaining the plaintext?
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61 views

Are the Common modulus attack, Common Factor Attack, and Wiener's attack different?

Is there a difference between: Common modulus attack Common Factor attack Wiener's attack or are these just a different name for the same attack?
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1answer
47 views

Difference between eavesdropping and traffic analysis

I was wondering what is the conceptual difference between these two passive attacks on a network. I was reading about them on Wikipedia and they seem quite similar to me. Is there a difference?
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1answer
62 views

Fault attack on RSA-CRT

I am trying to understand fault attack on RSA-CRT, and I found some example, which I don't know how to solve it. I know public modulus $N$, public exponent $e$, a value of faulty signature (where ...
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105 views

Attack on RSA when I know $e$, ciphertexts $c_1, c_2$ of the same message $m$ with 2 coprime modules?

I know that the same message $m$ was sent to two people resulting in ciphertexts $c_1, c_2$. The public keys are $n_1$ and $n_2$, $gcd(n_1, n_2) = 1$. And $e=3$ in both cases. How can I retrieve the ...
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2answers
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RSA: Should the generation of random data used for primes include zero

When generating random data that is later tested for primality, should the random data include the value 0x0? I would have thought that primes that do not include zero's are a subset of the set of ...
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1answer
61 views

Is forward search attack is the same as dictionary attack?

Currently, I started to learn about secure passwords in password file. The password file contains the hashed values for passwords. I know that the forward search attack for a password that if an ...
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73 views

Can perfect forward secrecy introduce vulnerabilities?

Is it always a win or could PFS algorithms introduce new attack vectors or weaken the level of secrecy vs not being used?
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245 views

What is the name of an attack where the compromise of one key compromises the whole system?

Consider the following: A whole system depends on the security of one private key and if this key is, for any reason, compromised, the whole system will be compromised. What's a suitable name for ...
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1answer
59 views

Regarding Lattice atttacks on ECDSA with a portion of known bits of the nonce k

I am new in the field of cryptography, and I am having some troubles understanding a concept regarding the lattice dimension needed in the attack on ECDSA using several messages with L known bits of ...
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1answer
87 views

How to prove that a rainbow table is complete?

Passwords that are hashed but not salted can be cracked using the rainbow table. I went through this and this which explains the logic behind rainbow table very well. But I am missing something about ...
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2answers
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side channel attack on RSA

A side-channel attack is any attack based on information gained from the implementation of Encryption protocol and by monitoring security-critical operations. Almost every encryption had a side-...
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1answer
38 views

what can attackers do between two end hosts

I have one question that I couldn't come up with a nice solution. So let's have this analogy, I have a box full of money and I want to deliver to this my friend. Here if we think of a potential ...
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29 views

Can someone give an example of no-message attack>

I know that a no-message attack IS THAT if the adversary has access to a signing oracle and a public key, he can sign an arbitrary message. So can someone give an example of this kind of attack?
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1answer
125 views

What is the difference between a forgery attack and an user impersonation attack?

I'm new to cryptography, so I was searching for a forgery attack, but unable to find anything. Can anybody tell me the difference between forgery attack and user impersonation attack?
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Cryptographic Attacks [closed]

I've been asked to write some course materials on cryptography and included in the objectives are some vulnerabilities/attacks. Most of these I have nailed but there are three that I don't seem to be ...
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24 views

Sample Information Set Decoding attack on McEliece Cryptosystem

I am trying to understand McEliece cryptosystem and attacks on it. Is there any basic example of Information Set Decoding attack on a toy example with small parameters like (7,4,1) ? I could not find ...
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1answer
43 views

What (if any) information can an eavesdropper infer in this scenario when using DES in OFB mode?

Assume that a company wants to use DES in order to encrypt messages to remotely control its manufacturing machines. The company uses different messages types of 8 ASCII characters length each. The ...
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What will happen to existing cyphertext when today's encryption is broken? [closed]

Even optimistically, I think we can all agree that many encryption algorithms that are widely used in production today will be "broken" sometime in the next decades. With "broken", I mean that (...
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2answers
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Self signed certificate for mobile app and backend from same company

My company's product is Android and iOS mobile app which connects to our own backend. All interactions of the mobile app are with backend developed by our own company. In such a situation, can the ...
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97 views

ElGamal with weak public key

Assuming this setup: A prime $p$, a generator $\alpha$ in $\mathbb{Z}_p^\ast$. Alice chooses her private exponent $d$ from $[2, p-2]$ and calculates her public key $\beta$ = $\alpha^d$. Bob then ...
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Bleichenbacher RSA1024 signature forgery, closed-form solution

Hal Finney's writeup (Bleichenbacher's RSA signature forgery based on implementation error) shows a formula for RSA3072. I tried to replicate the attack for RSA1024 and failed, since the first term of ...
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1answer
80 views

Statistical attacks on a list of MD5/SHA-1 hashes?

I have a list of MD5 and SHA-1 hashes where the input string is of the form secret1000 secret1001 … all the way up to ...
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1answer
86 views

Birthday problem applied to hash function with partition of the input set

I am not able to understand why if we consider a regular hash function, it is possible to say that we are partitioning the starting set and then apply the the birthday paradox/problem. Can anyone ...
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35 views

(Side channel) attack on a PIC18 micro controller

I'm trying to get some practical experience on (side channel) attacks. First I want to note all possible vulnerabilities. I thought about: Preset I have physical access and I own/wrote the software, ...
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2answers
81 views

Bellovin ESP Attack on UDP Packets

In Bellovin's ESP Attack, it is stated that: If $L_A$, $L_B$ are using UDP, attack is easier: Wait till session ends Allocate $L_B$'s UDP port to $X_B$ Replay all packets So, how ...
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1answer
449 views

Decryption of a file encrypted by pseudo-random number generator (The Linear Congruence rand()

How to decrypt this file: https://drive.google.com/open?id=1gZCujDYmEL-FZ5o_xBUS-Ng5979HSsZ7 Given that the only information available about it are: It has been created ‎on 21/3/‎2018, ‏‎9:05:15 AM ...
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Difference between fault measurement and fault model

In the context of fault attacks. What is the difference between fault measurement and fault model? I am reading a lecture and I can not understand for what measurement is used? Could you help me ...
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1answer
435 views

RSA attack with continued fractions (Wieners attack)

I found an article on the internet about an RSA attack with continued fractions. Given are the following numbers: $n = 205320043521075746592613$ $e = 70760135995620281241019$ $\frac{e}{n}=[0;2,1,...
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158 views

Unknown key-share attack

In the unknown key-share attack a dishonest entity C tempts two honest entities A and B to establish a key shared between them. At the end of the attack, A believes she shares the key with B, but B ...
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In RSA, how can we observe the message with given two co-prime public keys and same n value? [duplicate]

I am not sure if the title is clear enough. Here is question's body: Alice and Bob are very good friends and they share the same RSA modulus n. Of course, to have their own different public keys, ...
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286 views

RSA signatures that allow hash to move around in block

I'm looking at a broken RSA signature padding implementation in a real device. It's a very-badly implemented version of PKCS #1-like encoding, but before PKCS added the DER-encoded hash identifier. ...
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1answer
336 views

Is there any ECDSA Attack if I have millions of signatures?

I have been given the task to test the security of our company software. Our company software generates ecdsa signed supply order files. One can generate as many files as he wants. so my question is ...
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1answer
81 views

What is the reasoning behind the PRESENT key schedule?

It seems there are few books on PRESENT and even fewer that give any reasoning behind the mechanics of the key schedule. I understand how it works to the extent that I made a simple Excel program of ...
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1answer
911 views

If a key is used to encrypt that same key, is the computational cost to brute force it decreased?

If a key d is used to encrypt a message m that is identical to the key d, resulting in a cipher c c = encrypt(m, d) = encrypt(d, d) is the computational cost to brute force d lower than if the key d ...
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132 views

Enigma decryption with known plaintext and plugboard?

I have an enigma encrypted message with no known plaintext and a message with known plaintext. I also know that I, II, and <...
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0answers
64 views

Custom attack to CBC in IPsec

I have this exercise in my book and I got no starting point so far. We describe an attack of the CBC mode in IPsec. In this mode, a sequence of blocks $x = x_1, ..., x_2$ is encrypted with a key $K$...
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3k views

Is it possible to break SHA-512?

Is it possible to break the SHA-512 hash algorithm? Are there any successful attacks out there?
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299 views

Does blinding work against side channel on RSA?

In the so called "blinding" technique for RSA, prior to decryption, the ciphertext is multiplied by random $r$ raised to the power of $e$; e.g., $C$ is replaced with $C\cdot r^e$; and then after ...
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1answer
51 views

Is rekeying attack the same as related-key attack?

I've been searching about rekeying attack, but what I found is always using the term "rekeying/related-key attack". Is rekeying attack the same as related-key attack?
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1answer
44 views

What is the procedure to proceed towards breaking a cipher text when the process of encryption is not known?

I mean , if one is provided with a cipher text and the process of encryption through which text has has been encrypted has not been provided , then how is the cipher text broken ? Is frequency ...
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67 views

Question about key establishment protocol and key exchange attack

If an adversary $M$ observes a session of the protocol between $A$ and $B$ and learns the session key $k_{AB}$.How Can the adversary mount a successful impersonation attack and communicate with $B$ on ...
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1answer
114 views

Using round constants to thwart slide attacks

I'm partly unclear as to how the use of round constants in an iterated cipher makes it immune to slide attacks. I mean, I can see how it does from one perspective, but if the solution to slide attacks ...
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Are there any attacks on RC4 with skipped bytes? [duplicate]

I know that there are attacks on RC4 that allow the attacker to gain information about the key by looking at the first section of encrypted data. Many resources about RC4 encryption mention that ...
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1answer
614 views

How does the ROCA attack work?

I have been trying to understand the ROCA attack described here as the "First Attack" and I cannot follow the explaination. I have been trying to generate a 512-bits key and crack it. As far as I can ...