analysing cryptographic algorithms, potentially uncovering weaknesses in them (e.g. "breaking" them or casting doubts on their actual security)
2
votes
2answers
425 views
Cryptanalysis of Linear Feedback Shift Registers
It is well known that simple m-sequence linear feedback shift registers have a linear algebraic structure and therefore the generator seed can easily be deduced using the Berlekamp-Massey algorithm. ...
1
vote
1answer
158 views
Is there a security analysis of CryptDB?
Its interesting to see critical thinking being applied to cryptDB in contrast to all the hoopla around it here . cryptDB is not a major theoretical breakthrough but potpourri of technologies to make ...
0
votes
0answers
81 views
How to encrypt OpenVPN setup traffic [closed]
I have an OpenVPN server and a client that can successfully connect to said server. The traffic over the tunnel is encrypted. The tunnel works quite well.
However what is NOT encrypted (cleartext) is ...
3
votes
2answers
205 views
How can I break a Vigenère cipher with partial plain text?
I have an exercise to do regarding Vigenère encryption.
I've got the cipher text: WNZTNVIEEGTJYKRRWYUELWNZTNV
and a partial plain text: ...
0
votes
0answers
64 views
Need help with student project about IT security [closed]
I've been studying in university for computer security for 4 years.
All students have to make a course project by the end of year. And I have some problems with it.
I need help with the project's ...
20
votes
4answers
2k views
Is AES-256 weaker than 192 and 128 bit versions?
From a paper (via Schenier on Security's Another AES Attack) (emphasis mine):
In the case of AES-128, there is no known attack which is faster than the 2128 complexity of exhaustive search. ...
1
vote
1answer
294 views
AES encryption for images [closed]
Why AES based encryption is not recommended for encrypting images with high redundancy in their content? for example, the encryption of an image which shows a bird in the blue sky. Most of the pixels ...
0
votes
2answers
227 views
Cryptanalysis of S-DES - Equations
I am trying to derive equations for s and t in the cryptanalysis of a Simple DES algorithm, but I haven't been able to deduce it. I've attached an image of the portion that I'm referring to, and I'd ...
1
vote
2answers
273 views
Simply put, what does perfect secrecy means?
I would like to ask for a clear (but maybe not so deep) explanation of what the term "perfect secrecy" means.
As far as I have researched and understood, it has to do with probabilities of assuming ...
10
votes
3answers
545 views
How practical are side-channel attacks and how much of a concern are they?
I see a lot of research in very sophisticated side-channel attacks on crypto systems. Most (but definitely not all) seem to follow a trend, namely, the crypto system does something very dumb like ...
9
votes
2answers
256 views
Why is the salt used only once in PBKDF2, while the password is used often?
The purpose of PBKDF2 is to create a derived key (DK) from a master password (PW) and a salt, often using a function like HMAC-SHA256. I have read that the salt should be as random as possible. But ...
4
votes
2answers
1k views
How does a padding oracle attack work?
I am unsure of how a padding oracle attack works.
What I am not getting is how changing one bit at one time allows one to exploit(get keys) ASP.NET machines.
Can anyone explain this?
1
vote
3answers
217 views
How to encrypt data and know it will be secure for at least a few decades?
I want to encrypt a small amount (few kilobytes) of data and be fairly confident it will be secure against brute force decryption and advances in cryptanalysis for at least a a few decades (or more). ...
7
votes
4answers
1k views
What is the effect of the different AES key lengths?
How does a changing key length affects the ciphertext, not only in case of AES, but in general? I know that the key spaces become much larger and the number of rounds in case of AES changes, but is ...
0
votes
1answer
318 views
Cryptanalysing Affine cipher
I am trying to cryptanalyse a cipher–text encrypted by Affine cipher.
The encryption formula is: $c = f(x) = (ax+b)\bmod m$, where $a$ and $b$ are unknown constants; $x$ is a plain-text symbol, and ...
2
votes
1answer
109 views
What are the dangers of predictable (repeated) plaintext structures?
When using a "good", modern cipher (specifically one that provides ciphertext indistinguishability), is it a problem at all if there is some well-known structure in all plaintexts?
For example, ...
2
votes
2answers
247 views
Can I build a secure tweakable block cipher from a normal one by adding key and tweak?
Let (E,D) be a secure block cipher.
Consider the following tweakable block cipher:
...
0
votes
1answer
321 views
How to hack the new save encryption on ipad for uplink? [closed]
The new iPad version of Uplink appears to be using some new saving mechanic than the PC/Mac Version. Macs and PCs use 'RedShirt' but the iPad appears to instead be using 'SAV62' at the start of saves, ...
1
vote
1answer
171 views
Other than brute force, are there any attacks on Threefish-512 using only a single known plaintext block?
As per title, other than brute force, are there any attacks on Threefish-512 using only a single plaintext block? Are there any attacks like this in any other cipher?
1
vote
1answer
492 views
Deciphering a key from XOR encrypted cypher using boolean logic
Assume there's an unencrypted message A, and an encrypted message B. You know that message B was encrypted using a simple XOR method of A with a private key K, resulting in message B. Thus,
B = A ⊕ K
...
2
votes
2answers
954 views
How much computing resource is required to brute-force RSA?
It's been over 30 years since Rivest, Shamir and Adleman first publicly described their algorithm for public-key cryptography; and the intelligence community is thought to have known about it for ...
2
votes
2answers
136 views
Is there a way to compare the 923 bit pairing based key with RSA or AES, etc
I've see many articles, most of them basically the same, praising Fujitsu for cracking what is referred to as a 923 bit pairing based encryption. I understand that in comparing RSA to AES you've got ...
13
votes
1answer
389 views
Is this password migration strategy secure?
I want to upgrade the security of some existing databases of users' authentication tokens strictly for the purpose of making sure that if the database is stolen, attackers will not be able to guess ...
2
votes
1answer
181 views
Regarding matsui's Paper on Linear Cryptanalysis of DES
I's going throught the the Paper by Matsui on Linear Cryptanalysis of DES . In that he says
$NS_{5}(16,15)=12$
And then in the next paragraph he says considering the expansion and permutation phases ...
4
votes
2answers
203 views
Tunnels used in md5
I'm reading a paper about finding collisions for the MD5 hash algorithm involving the concept of tunnels.
But I couldn't understand about the difference between point of verification and point of ...
4
votes
1answer
143 views
Where can i find relative software for differential cryptanalysis?
Is there any publicly known software for differential cryptanalysis over some cryptographic building blocks as blocks ciphers or cryptographic hash functions
8
votes
3answers
2k views
What is the difference between known-plaintext attack and chosen-plaintext attack?
I am very confused between the concept of known-plaintext attack and chosen-plaintext attack. It seems to me that these two are the same thing, but it definitely is not.
Can anyone explain to me how ...
1
vote
2answers
157 views
How hard is to find the operators of an addition knowing the sum of them?
I want to learn whether or no there is a cryptographic primitive,scheme assumption that is based on the following hard problem if it is hard . By hard we mean that we have a polynomial adversary: The ...
6
votes
2answers
701 views
Why do block ciphers need a non-linear component (like an S-box)?
Why is there a requirement of "Non-Linear functions" as a component of many popular block ciphers (e.g. the S-box in DES or 3DES)?
How does it make the cipher more secure?
The only intuition I have ...
2
votes
2answers
297 views
How to get the keyword from a keyword cipher?
I was given a ciphertext and now I am trying to break it via looking for the keyword.
This is a keyword cipher. So:
PlainEnglish: ABCDEFGHIJKLMNOPQRSTUVWXYZ
If ...
1
vote
2answers
161 views
Brute force a ciphered message?
I wrote my own cipher to encrypt messages. I would like to test a sample ciphered message to see how strong it is. Are there any tools for such task either in Windows or Linux ?
