Encryption is the process of transforming plaintext using a cipher to make it unreadable to anyone except those possessing the key.
0
votes
1answer
120 views
Request for 1024-bit primes $p$ , subgroup $q$ and subgroup generator $g$
I need to find a prime $p$ of $1024$ bits with a $160$ bit sub group size $q$, such that $q|p-1$ , and $g$ is the generator of the sub group size $q$.
I'm looking for the numeric values of $p$ , $q$ ...
6
votes
1answer
426 views
How to break an arbitrary XOR and Rotation based encryption?
I heard encryption based purely on XOR and Rotation is inherently weak. The paper Rotational Cryptanalysis of ARX says:
It is also easy to prove that omitting addition or rotation is devastating, ...
-1
votes
1answer
121 views
How to bring little changes in DES algorithm
I thought of implementing DES modes of operation as a project...But my guide asked to change or to modify the DES algorithm in such a way to overcome drawbacks of DES...So is there any way to do ...
3
votes
2answers
181 views
Two step encryption
Is there any asymmetric cryptography algorithm which will allow recursive encryption.
...
0
votes
3answers
217 views
How to check the strength of an encryption algorithm?
I asking for advice on how to check strength of an encryption algorithm.
4
votes
1answer
103 views
What is 'security margin'?
I have been academic papers about Rijndael, Serpent, and Twofish, and there is this term that is vague to me. I cannot find a tangible definition in google. Can someone briefly define, describe, ...
-3
votes
1answer
114 views
AES implementation in java that allows key of 320-bit length [closed]
I need an implementation of AES(Rijndael) in java that allows use of a 320-bit key.
Please suggest a reliable implementation
1
vote
2answers
124 views
FIPS 140 compliance for encrypted files
Does FIPS 140-2 require specific key sizes, or does it have specific requirements for the data?
In other words, if I encrypt a file, how I can check whether it is FIPS-compliant or not? Does only the ...
2
votes
2answers
187 views
Why does the recommended key size between symmetric and assymetric encryption differ greatly?
In various articles it is mentioned that for secure communications, the recommended key sizes are 128-bit key size for symmetric encryption (which makes it $2^{128}$ possible keys?) and 2048-bit key ...
0
votes
2answers
152 views
Is such a crypto-system available?
$E(k_1, pt) = c_1, E(k_2, c_1) = c_2, D(k_{new}, c_2) = pt$, where $k_{new} = f(k_1, k_2).$ Sharing $k_{new}$ and $k_2$ should reveal no information about $k_1$.
Clarifications:
Being able to ...
1
vote
1answer
501 views
How do I derive the time complexity of encryption and decryption based on modular arithmetic?
I want to calculate the time complexity of two encryption and decryption algorithms.
The first one (RSA-like) has the encryption
$$ C := M^e \bmod N $$
and decryption
$$ M_P := C^d \bmod N. $$
...
2
votes
1answer
156 views
Visualization of cryptography
I think CrypTool is great software. And what I find most useful in it is visualization of algorithms such as Caesar, Vigenere, AES, DES. And my question is: does anyone know other tools which are ...
1
vote
1answer
100 views
How can encryption software accept password lengths which are not one of the AES key lengths?
AES comes with key sizes of 128, 192, and 256 bit.
But in Truecrypt or other crypto software we can use passwords of different length, even less than 128 bit or more than 256 bit.
How is this ...
4
votes
3answers
149 views
What is a block cipher?
I have read about block ciphers, but I do not understand the topic completely.
Is a block cipher a way to send data or a way to encrypt data?
How is the data divided into multiply blocks before it ...
0
votes
0answers
49 views
How compute encrypt and decrypt runtime for agorithm [closed]
I programming RSA algorithm is the following two function in java language in my thesis
...
2
votes
3answers
65 views
Secure communication between multiple peers on a public channel
I am wondering how can I secure communications between multiple peers over a public channel, like an IRC channel. With two peers it is easy - they exchange their encryption keys and decrypt the secret ...
-2
votes
1answer
62 views
Cryptographic Primitive Method
Is there any cryptographic primitive bijective (one-to-one and onto) function for creating cryptographic tools like symmetric encryption/decryption, Hash code generator, MAC, HMAC and Random number ...
2
votes
1answer
90 views
Hashing a password with the password?
I was wondering if hashing a password with the password would be a good way of encrypting the password. So, the user must know his/her password to get the same result as the one in the database. Also, ...
5
votes
5answers
346 views
Using CBC with a fixed IV and a random first plaintext block
What if, instead of using CBC mode in the normal way with a random IV, I used this approach:
Use a fixed IV (like a block of 0's).
Before encrypting, generate a random block and prepend it to the ...
2
votes
0answers
46 views
Encrypting or HMACing password digests
Assuming I'm using bcrypt to digest passwords, is any additional security gained by either encrypting or HMACing the resulting digests? By requiring a key to compare password hashes, I would expect ...
0
votes
0answers
55 views
How compared encryption algorithm in terms of efficiency
I doing to compare two algorithm cryptography. first algorithm is RSA cryptography and second algorithm is El Gamal elliptic curve cryptography. now I want a way to compare between two algorithm by ...
2
votes
1answer
99 views
What does a “cycle” mean in cryptography benchmarks?
In this table, for example, cryptographic algorithm performance is measured in cycles per byte for symmetric ciphers, and in cycles per operation for asymmetric ciphers.
What does "cycle" here mean, ...
4
votes
1answer
83 views
Two way encryption with random IV
I'm attempting to encrypt some information into our database to be later pulled back out and displayed to the user. Searching and reading up on different methods I found a post over at stack exchanged ...
3
votes
1answer
276 views
What happens if an RSA key pair has identical public and private exponents?
Rather, is it possible for big prime numbers?
Classroom examples usually involve smaller primes, so for example if you are given a prime number pair $p = 3$, $q = 13$ you would get $n = 39$ and $e = ...
4
votes
2answers
164 views
Is it possible to break a hash-based block cipher?
Let's define the following block cipher:
$C_n = M_n \oplus H(k + n)$ where $C_n$ is the nth block of ciphertext, $M_n$ is the nth block of plaintext, $H$ is a cryptographic hash function, and $k$ is ...
5
votes
4answers
384 views
Creating an encryption key from several other keys and using hash functions
I want to combine two or more keys to create a single encryption key that relies on all of them. What is the proper method for doing that? Simple XOR? Using hash functions? Something else?
I ...
6
votes
2answers
499 views
Why is ciphertext from low entropy plaintext not compressible?
This comes following a discussion with a colleague.
My plaintext file plain consists of a about 100,000 lines of "all work and
no play...". It's size is: 2.2 MB.
...
2
votes
2answers
389 views
Why is asymmetric cryptography bad for huge data?
I've been told that asymmetric cryptography requires that the message to be encrypted be smaller than its key length.
Why is this?
I know about hybrid encryption, which uses symmetric encryption to ...
-1
votes
1answer
101 views
Needing to encrypt plain sight information
Okay here are my requirements.
I need a solution that can do the following.
Lets say I have an encrypted piece of text with the value "20".
and I have UserA and UserB
I give UserA the Keys (/5 and ...
3
votes
3answers
527 views
How will Cryptography be changed by Quantum Computing?
I realise this isn't a 'yes or no' question, and I apologise for asking something that could be seen as a discussion thread, but I had to ask.
I'm currently doing an EPQ in CS (specifically how QC ...
1
vote
3answers
117 views
Public keys and their protocols
I'm having difficulties understanding exactly what this protocol means:
$S \to D : \{N_S , S\}K_D$
$D \to S : \{N_S , N_D \}K_S$
$S \to D : \{N_D \}K_D$
"where $S$ represents the supervisor’s ...
4
votes
1answer
123 views
Future-Proof Versioning and Validation
I am working on a library (using standard primitives: AES256 CTR; HMAC with SHA256; PBKDF2 with SHA256, 128 bit salt, and 10000 rounds) to encrypt and decrypt data, given a password.
The encrypted ...
2
votes
1answer
189 views
Proving that a scheme is not IND-CPA-secure
Suppose I want to prove that a given symmetric encryption scheme is not IND-CPA secure. The first thing I do is to define a specific adversary that attacks the scheme. How can I proof neatly, (using ...
3
votes
1answer
154 views
Is there a field guide to ECC for the IT Security layman?
I'm trying to understand ECC from an IT layman's perspective and am trying to separate the theory from the standards, and understand why certain features are implemented or not implemented in the ...
0
votes
0answers
52 views
Intorduction to AES basics and where do i get online material [closed]
I'm final year undergraduate, i came across this encryption standarad and when i met my professor about this encyption standarad, he said ok go on with it, but he is not willing to guide me from ...
2
votes
1answer
276 views
Self-expiring symmetric keys, or: cryptography in absence of secure deletion
I can encrypt some data D using a random symmetric key K, obtaining a ciphertext C, and then encrypt K with my public key Pub and obtain H. So far so good: I can only decrypt C if I have H and my ...
2
votes
1answer
76 views
Individual bits of Textbook RSA
This question relates to the underlying RSA assumption. Forgetting about the fact that Textbook RSA is deterministic, I am curious about the assumed strength of the RSA problem.
Does RSA hide all ...
2
votes
1answer
235 views
How much extra information is in an RSA public key?
I'm trying to calculate the size of an RSA public key in Ruby. I've retrieved the key in PEM format, and once I've decoded the base64 part from the PEM format, I get the size in bytes. What I find is ...
3
votes
1answer
210 views
A single password manager vs password generator/hash
I have been wondering about the options available for managing passwords. However, they all seem to fail if the master password is compromised (which isn't a big surprise).
On one hand you have ...
2
votes
2answers
125 views
Information leakage in real-time voice encryption
I saw some time ago a post discussing the issues surrounding encryption of speech/voice in VoIP and how it can leak information (can't find it now). Can someone provide an insight into some of the ...
1
vote
1answer
144 views
Can a shift cipher attain perfect secrecy?
On a practice question for my intro cryptography exam, it asks the following:
Assuming that keys are chosen with equal likelihood, the shift cipher provides:
A) computational security
...
5
votes
1answer
199 views
Are there any Implementations of Secure Indexes?
There are several papers about Secure Indexes, for Example "Searchable Symmetric Encryption:
Improved Definitions and Efficient Constructions" and "Secure Indexes". ...
-2
votes
1answer
124 views
Securing a lookup table [closed]
I am looking for a secure approach to handing the following situation:
You're given a string that means something. It contains parts of something larger, each of which is clearly understood. For ...
3
votes
1answer
450 views
Compare Blockmode CBC (with diffuser) against XTS
I have some problems in understanding the "advantage" of AES-XTS compared to CBC with diffuser.
I read something about FileVault, in this paper they mention the two modes of operations XTS and CBC ...
27
votes
4answers
6k views
What are the practical difference between 256-bit, 192-bit, and 128-bit AES encryption?
AES has several different variants (AES-128, AES-192, AES-256), but why would I use one over another?
4
votes
1answer
153 views
In RSA encryption, does the value of e need to be random?
I am a novice programmer and am just finishing up an RSA encryption program that I am writing for practice. Currently I have the program generate a relatively small random value for the public key e. ...
1
vote
1answer
125 views
What's a good P to use in ElGamal key generation?
I need to generate a 1024 bit ElGamal key on Android, and key generation takes forever (~10 minutes on a Galaxy Nexus), I suspect because it take so long to generate a safe prime.
Is it dangerous for ...
3
votes
3answers
599 views
Why is the IV passed in the clear when it can be easily encrypted?
The initialization vector (IV) is exclusive or'd against the plain text before encryption for the first block sent in order to prevent an attacker from learning that duplicate message blocks are being ...
3
votes
2answers
112 views
Is there an advantage to storing keys split between several hashes?
I have a question about the way to store a key or password that was used for encryption, so that the application can check if the user put in the right key for decryption. If I make a mistake, please ...
-4
votes
3answers
149 views
Why shouldn't one build a MAC by XORing multiple message blocks?
I found this simple proposal for a MAC algorithm:
Let the MAC of message M (which consists of message blocks $M_1$,$M_2$, ..., $M_n$)
be the AES encryption with key K of the XOR of all the ...
