Encryption is the process of transforming plaintext using a cipher to make it unreadable to anyone except those possessing the key.
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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
504 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
$$ M_P := C^d \bmod N. $$
...
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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
...
1
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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 ...
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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
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 ...
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 ...
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, ...
2
votes
0answers
47 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
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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 ...
6
votes
1answer
430 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, ...
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 ...
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, ...
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votes
1answer
330 views
Is a steganographic technique which has a universal decoder novel/secure? [closed]
I've come up with an approach to steganography which needs review of both its cryptography and its math. There's a complete working implementation at https://github.com/bramcohen/DissidentX and the ...
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 ...
4
votes
3answers
338 views
How and why can a decryption program tell me that a key is incorrect?
I have noticed that some programs used for file encryption will tell you if an entered key is wrong when you try to decrypt. It seems (to me at least) that this would mean that the key somehow is ...
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 = ...
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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 ...
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
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 ...
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 ...
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
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 ...
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 ...
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 ...
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 ...
1
vote
1answer
145 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
...
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 ...
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 ...
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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
453 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 ...
3
votes
2answers
181 views
Two step encryption
Is there any asymmetric cryptography algorithm which will allow recursive encryption.
...
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
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 ...
5
votes
2answers
133 views
Will varying plaintext compensate for a fixed initialisation vector?
This is a follow-up question to Relative merits of AES ECB and CBC modes for securing data at rest.
I need to store encrypted Personal Account Numbers (PANs) in a database. The only encryption option ...
5
votes
5answers
348 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 ...
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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 ...
2
votes
1answer
2k views
Difference between stream cipher and block cipher
A typical stream cipher encrypts plaintext one byte at a time, although a stream cipher may be designed to operate on one bit at a time or on units larger than a byte at a time.
A block cipher ...
0
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1answer
173 views
How does a client verify a server certificate?
As far as I know,
when I request a certificate from Verisign (for example), and after they approved that me is me, they create a certificate (for me) which contains the digital signature and public ...
0
votes
1answer
247 views
Is it possible to crack a blowfish 256 bits encrypted file?
I have a file of my own that i have encrypted using Coder-Abi. Now i can just remember part of this password. So, would it be possible (much easier) for me to crack it knowing only part of it? I can ...
2
votes
2answers
304 views
Constructing a block-cipher from a hash function
It is possible to use a hash function to construct a block cipher with a structure similar to DES? Because a hash function is one way and a block cipher must be reversible (to decrypt), how is it ...
2
votes
1answer
406 views
Advantage of AES(Rijndael) over Twofish and Serpent
I'm trying to figure out a suitable encryption technique and after reading a bit, I figured the current AES 128-bit encryption is suitable for what I'm trying to do. However, this is more due to the ...
1
vote
1answer
161 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
101 views
Is tokenization really alternative to encryption? [closed]
Much is being written all over the web that Tokenization is an alternative to encryption here , here and here
Is there some literature in crypto community on the same ? on formal treatment of ...
0
votes
0answers
89 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 ...
0
votes
1answer
380 views
What is the most secure encryption algorithm? [JS/PHP] [closed]
Lets say I have a web page with a form on it. There is javascript to submit the form after doing encryption. The encrypted string from the text box gets sent visibly to the server, which is running ...
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
2answers
117 views
CPA Secure Chosen plaintext scheme
The example for IND-CPA secure schemes given is generally:
for a random r,
Enc_k(m) =(r|| E_k(r) XOR m) where E is a PRF
But does the role of r and k really matter--i.e. isn't this equally ...
3
votes
2answers
111 views
Distinguish messages
Since i cannot comment on questions, I give my own:
If a secret key encrypt algorithm can encrypt messages of arbitrary length and the encrypt algorithm is probabilistic then: suppose the adversary ...
