Encryption is the process of transforming plaintext using a cipher to make it unreadable to anyone except those possessing the key.
0
votes
2answers
107 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
2answers
62 views
Why this k parameter is in unary in adversary PPT algorithm? [duplicate]
While reading some text on cryptography, I found that algorithm $A$, that the adversary (called Eve by convention) runs to break the cipher message, needs two parameters, candidate message ($y$) and ...
3
votes
1answer
94 views
Alternatives to HMAC + CBC?
I'm looking at using HMAC + CBC. The combination looks like this:
ciphertext = AES256(text, k1)
data = HMAC-SHA256(iv | ciphertext, k2) | iv | ciphertext
Where:
...
0
votes
2answers
82 views
Generate fixed length cipher text from arbitrary length plaintext
Using an encryption algorithm like AES, is it possible to generate a fixed length cipher text no matter how long the plain text becomes?
-1
votes
0answers
38 views
How to decipher this morse-like code message? [closed]
I found this little string that looks like Morse Code, but instead of dots (dits) has hearts symbols, I tried to change the hearts for dots, but I was not able to get any redable text.
...
-3
votes
1answer
68 views
Can someone help with the following hashes? [closed]
Here are a couple of hashes. I feel it should be easy (simple base conversions?) to decode them but I haven't succeeded so far. Can someone help?
...
1
vote
1answer
78 views
Security of Salsa20 with some known plaintext?
Basic question- if I'm encoding a bunch of known filetypes with salsa20, will it still be secure if the plaintext header is known?
Assume that a different IV and Key are generated before each file is ...
0
votes
0answers
27 views
Decrypting TLS in Wireshark when using DHE_RSA ciphersuites [migrated]
How can I decrypt TLS messages when an ephemeral Diffie-Hellman ciphersuite is used? I am able to expose the premaster secret and master secret from the SSL Client. Using that, how to decrypt the ...
1
vote
1answer
120 views
Indistinguishability attack example
I want solve the next exercise. The author defined the experiment for the cryptosystem $\Pi$, the adversary $A$ and the security parameter $n$ as follows
$\mathsf{PRIV_{EAV}}(\Pi,A,n)$
The ...
-1
votes
1answer
84 views
What length should the padding be when encrypting or signing with RSA?
Does it matter what length the padding is? If so - what length should it be?
(Another point: Should it be random?)
1
vote
1answer
103 views
Encrypt a single file, chunk-by-chunk, each chunk using different key (AES)
Encrypt a single file, chunk-by-chunk, each chunk using different key.
I am a security newbie (only took 2 security courses before)
But currently I am using this encryption method for my Android ...
-1
votes
2answers
55 views
Book Didactic Security Notions [closed]
I want study more about cryptography reading papers, but I have a problems to understand few concepts: security notions, random oracle model, IND-CCA, ... etc. I began study this concepts by internet: ...
1
vote
1answer
67 views
How to compare two datasets „anonymously”?
Ok, I hope this question makes some sense because I am not so sure how to word it any differently… Imagine the following situation:
There are 10 defined colors (blue, orange, yellow etc.)
There are ...
0
votes
2answers
208 views
Custom crypto library in C
I will be making (in the near future) an app that will contain some pretty heavy crypto. As it is possible that my app will be ported to different devices (initially it will be iOs only, but Mac, ...
-1
votes
1answer
40 views
Determine the Identity of Caller [closed]
Let me explain my situation.
I have a provider which is made up of a registration page and a web service. Online vendors (clients) register with the provider by providing details such as username, ...
0
votes
1answer
92 views
RSA - Ecrypting the same data with the same public key = same ciphertext?
If an adversary knows my public key and guesses what was my plaintext, can he test for it somehow?
The most obvious way is encrypting the guessed plaintext with my public key and the same parameters ...
3
votes
1answer
137 views
Secure encrypt-then-sign with RSA
I understand that when you want to encrypt and sign data with RSA the generally recommended approach is sign-then-encrypt.
However, I have encrypted data that I need to sign, to prove the author of ...
1
vote
0answers
63 views
Is OAEP reversible?
Given nothing more than some integer $m =$ OAEP($M$), is it possible to recover the original plaintext $M$? In other words, without being given the hash functions or the random string used for ...
3
votes
1answer
81 views
implementing long term archive encryption
Let's say I want to create private archives for the long term (e.g. more than 30 ). The archives' sizes could be anywhere from 1 GB to 30 GB. As far as I understand I could go down two ways:
The ...
-4
votes
0answers
63 views
RSA Encryption Sckeme [closed]
Can anyone help me with this question?
A and B want to exchange encrypted messages; specifically, B wants to send a message M
written in binary format to A, which needs to be encrypted. They agree on ...
4
votes
1answer
199 views
repeating-key xor and hamming distance
I read that to break repeating-key xor you can do the following: try a keysize $n$ and compute the hamming distance between the first $n$ bits of the encrypted string and the bits $n+1$ to $2n$ of the ...
3
votes
1answer
111 views
Combining AEAD with RSA
'Hybrid' encryption, where we combine symmetric encryption with public-key cryptography, is pretty 'tried and tested'.
To summarise, we generate a symmetric key and encrypt it using RSA. We would ...
-1
votes
0answers
25 views
Create groups of keys [closed]
I looking for a solution to encrypt, sign documents or email a key group and send to one customers. The group of keys are had already created user keys and I would like to use them.
Is not an option ...
3
votes
2answers
71 views
GPG and PAR2 error correction data from the plain archive, will it compromise security?
I have the following scenario:
Archives compressed with 7z, hundreds of MiB in size
GPG to encrypt the archives (binary, without ASCII armor)
PAR2 to create error correction data
Question
1. ...
2
votes
2answers
101 views
Keys required for cryptography
I am reading an article on cryptography at following location:
http://www.entrust.com/resources/pdf/cryptointro.pdf
Historically, encryption systems used what is known as symmetric cryptography. ...
2
votes
0answers
66 views
How can I prove that this encryption scheme from a random oracle is secure?
I am reading this example:
A random oracle is an ideal object.
What makes a random oracle convenient for proofs is the part about knowing nothing on the output for a given input if you do not ...
0
votes
2answers
68 views
ElGamal: Generation of “g” value?
I haven't been able to find a clear explanation on this (and I'm probably just confused in general). I have the following parameters of ElGamal signatures:
$p$ = safe prime
$q = (p-1)/2$
$g$ = an ...
2
votes
1answer
73 views
Why unit vectors should be encrypted bit per bit in that case?
At this work at section $2.2$ concerning a possible application for the BGN cryposystem the author points out that if you want to encrypt a unit vector $\overrightarrow{u_l}$ of size $l$ then the ...
0
votes
0answers
19 views
ECKS-PS algorithm: searching in encrypted data; bilinear maps [duplicate]
I have found an encryption algorithm named ECKS-PS (published in a paper named 'efficient conjunctive keyword search on encrypted data storage system', written by Jin Wook Byun, Dong Hoon Lee, and ...
0
votes
1answer
90 views
ECKS-PS algorithm: searching in encrypted data; bilinear maps
I have found an encryption algorithm named ECKS-PS (published in the paper Efficient conjunctive keyword search on encrypted data storage system) that allows an user to search in encrypted data. All ...
1
vote
1answer
72 views
Ciphers in CBC mode reveal place of change in plaintext
Theoretically, when using a symmetric block cipher in CBC mode, the current block is dependent on the previous block. Suppose one plaintext is encrypted using CBC, and then one bit of it is changed, ...
2
votes
1answer
53 views
Why constrain the message lengths in indistinguishability in the presence of an eavesdropper?
I need your help with a very basic concept in cryptography which I can't understand/prove on my own.
I'm trying to prove and understand why, under "indistinguishability in the presence
of an ...
2
votes
2answers
134 views
How can mega store my login details and still be secure?
I understand how Mega's encryption works. For a quick summary of all those in the future looking for an answer on this... here is how it works:
Upon first signing up for an account you make a ...
1
vote
1answer
91 views
What's the difference between Trapdoor Functions and Encryption Functions?
From Wikipedia:
A trapdoor function is a function that is easy to compute in one
direction, yet believed to be difficult to compute in the opposite
direction (finding its inverse) without ...
4
votes
1answer
98 views
Client and server using same SSL certificate - any issues?
I'm working on software where multiple components will communicate with each other using SSL.
There would be one central component acting as a server, which would also require the clients to present ...
5
votes
1answer
98 views
Using encryption schemes for identification
I've been researching how to implement a post-quantum SSL-like connection authentication, especially correct identification&authentization of the server/client. Because good post-quantum digital ...
1
vote
2answers
78 views
Can two rc4 encoded messages be XORed and decrypted if encrypted with the same key?
If I have the following:
E1 = RC4(M1, K);
E2 = RC4(M2, K);
If two different messages M1 and M2 are encrypted with the same key, K, can the key be recovered by ...
2
votes
2answers
146 views
Assymetric password encryption - Viable? Which algorithm?
We have an application that requires cleartext passwords for user authentication because of the authentication mechanism in use (RADIUS/CHAP), which unfortunately we cannot change. Since we don't want ...
0
votes
1answer
78 views
In which disciplinary kind can Cryptography be put?
Is it a multidisciplinary? an interdisciplinary? a cross-disciplinary? or a trans-disciplinary?
what are the basis put to describe each kind?
I mean how can we infer by which disciplinary field we can ...
2
votes
1answer
115 views
How to compute the dot product on encrypted values?
Is there a practical homomorphic encryption scheme that can give reasonable execution time results in computing a dot product:
$$a_1*b_1 + a_2*b_2 +a_3*b_3 +\ldots+ a_n*b_n$$
I imagine the scheme will ...
2
votes
1answer
104 views
Cracking an RSA with no padding and very small e
I have a project wherein i have to crack a given cipher text encrypted using RSA and have been given N and e. Can someone suggest an RSA attack using a very small exponent e(here e=3) and no padding?
0
votes
1answer
71 views
Encrypting and Decrypting a 19-digits long BigInteger
How can I take a maximum 19-digits long BigInteger and encrypt it with the following rules:
The result must be based on digits and lower-case English letters ...
1
vote
2answers
122 views
Security of Deterministic Encryption Scheme
A deterministic encryption scheme is a cryptosystem which always produces the same ciphertext for a given plaintext and key, even over separate executions of the encryption algorithm.
Although we ...
6
votes
1answer
155 views
How would one crack a weak but unknown encryption protocol?
I asked a question on security.stackexchange, but was told it would be a better fit here:
http://security.stackexchange.com/questions/32779/how-would-one-crack-a-weak-but-unknown-encryption-protocol
...
-5
votes
1answer
32 views
decrypting unreadable string [closed]
Does anyone recognise this type of encryption? These are phone numbers consisting of 10 digits and starting with 0 but the encrypted text width is not 10 and does not start with the same character.
0
votes
1answer
46 views
Solving congruences using PARI
I'm having trouble finding info in the docs about how to solve a system of congruences. The closest I can find is 'matsolvemod' in here: ...
1
vote
1answer
53 views
What is total key space in transposition algorithms
How we can measure key space in transposition algorithms? Should we specify the method, like rail fence ?
2
votes
1answer
184 views
Low Public Exponent Attack for RSA
I'm having trouble understanding the algorithm for finding the original message $m$, when there is a small public exponent. Here is the example I'm trying to follow (you can also read it in the 'Low ...
2
votes
1answer
212 views
Is AES-256 a post-quantum secure cipher or not?
We know Grover's algorithm speedup brute-force attacks two time faster in block ciphers (e.g brute-forcing 128 bit keys take $2^{64}$ operations not $2^{128}$).
That explains why we are using 256 bit ...
0
votes
2answers
104 views
Strong encryption done by hand [duplicate]
One of the distinguishing features of a good encryption algorithm, is that it is easy to encrypt, and hard to crack. Are there any that are easy enough for average folk to remember, and calculate by ...
