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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2answers
295 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
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1answer
380 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 ...
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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 ...
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0answers
97 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 ...
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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 ...
0
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1answer
349 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
183 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
113 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
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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 ...
0
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1answer
64 views
Initialization value (IV) bit error
When a bit error happens in an IV, what would the result of decrypting a cipher-text be in the different encryption modes like ECB, CBC, CFB, OFB, and CTR?
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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 ...
2
votes
1answer
194 views
Can ElGamal encryption and ElGamal signatures be used together sharing the same key-pairs?
I'm working on a encryption system where each party can store exactly a single ElGamal private key in a device. This is a hardware limit. The system must be expanded to support signatures and ...
0
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4answers
322 views
“Padless” One-time-Pad encryption
I have just read about the perfect security of an OTP encryption and what came to my mind was that what if the Pad used for encryption/decryption did not have to be transported separately from the ...
2
votes
1answer
343 views
Why, or when, to use an Initialization Vector?
i'm trying to figure out when an Intialization Vector (IV) should be used.
There are anecdotal reports that WEP was broken because of weak IV's. It's also claimed that if two pieces of plaintext are ...
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2answers
205 views
Why is an Encrypt-and-MAC scheme with deterministic MAC not IND-CPA secure?
I'm preparing myself to exam, but I have a lot of troubles with rigorous proofs. It's the task from two-years ago exam. At the bottom I reminded one definition.
Let $(Gen_E,Enc,Dec)$ be an ...
1
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1answer
124 views
Messages of different lengths and one-time computationally-secret
I'm preparing myself to exam, but I have a lot of troubles with rigorous proofs.
Let $\Pi=(Gen,Enc,Dec)$ be an efficient secret-key encryption scheme that is not fixed-length. That is, for any $n$ ...
1
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4answers
344 views
How easily could this be cracked?
I'm looking into encrypting files like this: First, I SHA-1 hash the password. Let's say the password is something normal like "hello123", and then hashed. Then I encrypt a file using this:
...
2
votes
2answers
281 views
Why is a non fixed-length encryption scheme worse than a fixed-length one?
I have the following definition (highlights by me):
An (efficient secret-key) encryption scheme $(Gen,Enc,Dec)$, where $Gen$ and $Enc$ are PPT algorithms and $Dec$ is a Deterministic Polytime ...
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1answer
194 views
Problems with implementation of ElGamal using OpenSSL [closed]
I recently did an implementation of a semantically secure modification of ElGamal using OpenSSL. I'm implementing part of a book that i have, and several parts of the book do not agree with things ...
0
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0answers
57 views
What is this encryption algorithm? [closed]
I have a crashed old JSP system, while recovering I stopped since I am not able to find the right 2-ways encryption algorithm (OR encoding), so I need your help, below some examples of inputs and ...
20
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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. ...
0
votes
2answers
200 views
Key derivation from a random seed
The main problem is to use a block cipher to generate a random key.
I would like to generate 256-bits key which can be as random as possible. I generate it in the following way:
Pick a plaintext ...
1
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1answer
295 views
How can I implement the “Multiplication Modulo” and “Addition Modulo” operations in IDEA?
I am currently working on IDEA (International Data Encryption Algorithm), and I don't know how to perform Multiplication Modulo and Addition Modulo.
This is how IDEA operates:
IDEA operates on ...
2
votes
2answers
127 views
How to construct a variable length IND-CPA cipher from a fixed length one?
Suppose we can construct a secure (IND-CPA) encryption scheme for fixed length messages. I was wondering if there is a natural way to extend this construction for messages of variable length such that ...
0
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1answer
155 views
Key Scheduling of International Data Encryption Algorithm (IDEA)
How to perform the key scheduling in International Data Encryption Algorithm (IDEA),
I took a research but I can't understand how to perform it,
"further groups of eight keys are created by rotating ...
1
vote
1answer
327 views
Traditional DES scheme in Unix crypt function
In a security context course, we need to reproduce the old DES hashing scheme in the crypt program, on an old unix system.
I am actually reading the crypt page on wikipedia:
The traditional ...
2
votes
2answers
142 views
Can I save space for short messages by using encryption with private key instead of a signature?
Let's say I have a message, a Private Key and a Public Key.
Normally if you want to see if the message is unaltered and is from the sender you would have the message part + signature part, which you ...
2
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0answers
190 views
How do I encrypt with the private key? [duplicate]
Possible Duplicate:
RSA encryption with private key and decryption with a public key
This wording is creeping everywhere (e.g. there): "I encrypt with the private key" and even sometimes, ...
0
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0answers
106 views
How is TrueCrypt in-place system drive encryption implemented? [closed]
TrueCrypt supports encrypting a system partition while operating system is running.
From the docs:
Note that TrueCrypt can encrypt an existing unencrypted system
partition/drive in-place while ...
1
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2answers
95 views
Encryption algorithm which produces comparable results for substrings
I am wondering is there any encryption algorithm available which produces comparable string.
I am expecting the output as shown below.
...
1
vote
2answers
117 views
RSA keys finding when messages are known
I have this situation, where, in a game, people send messages to each other (game moves etc...) These messages need to be encrypted, and should only be readable by the destination person. I am using ...
1
vote
1answer
292 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
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0answers
110 views
How do you ensure that a large remote file is encrypted? [closed]
On a general level, is there any way to ensure that a file has been encrypted? Specifically, is there any way to check this remotely using something like a checksum or key?
Here's a simplified ...
1
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2answers
214 views
Avalanche noise RNG for one-time pad use
I came across this little HRNG widget and was really intrigued as I have been looking for a decent but afordable source for truly random bits to use in a one-time pad.
The question is, would a HRNG ...
2
votes
2answers
251 views
Perfect security definitions
In my notes, there are 2 definitions of perfect security:
"For $M \in \{0,1\}^m$, define the distribution $D_M$ on strings as follows: to choose a random member of $D_M$, choose a random $K \in ...
1
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1answer
258 views
One-time pad and zero key
I'm doing some exercises before my exam, and I am stuck with task number 4 in this file: http://www.cs.umd.edu/~jkatz/crypto/f10/hw1.pdf
Could you help me with this task?
When using the one-time ...
2
votes
5answers
296 views
How to encrypt a short string and keep the length secret
I need to encrypt relatively short strings (generally less than 100 characters). If possible, I want to avoid leaking the length of these strings. How can I do that?
The thing that came to my mind is ...
9
votes
1answer
219 views
What is the theoretical and practical status of mental poker?
I'm able to find a lot of scattered papers on the development of mental poker since RSA proposed the initial solution but no recent report (i.e. after 2005) on what is the status of the problem, eg:
...
6
votes
2answers
340 views
What's is the main difference between a key, an IV and a nonce?
What are the main differences between a nonce, a key and an IV. Without any doubt the key should be kept secret. But what about the nonce and the IV. What's the main difference between them and their ...
0
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2answers
207 views
Could the Enigma algorithm be classified as a Feistel network?
The Enigma algorithm is a encryption method that was developed (I believe) by the Germans in WWII. It went a little something like this:
When a letter was typed on the keyboard of the Enigma ...
1
vote
2answers
88 views
When is each key used when encrypting an email using OpenPGP?
When you send an email using PGP to encrypt emails, is the recipients public key used to encrypt the email, or is your private key used? Are they both used?
At what points do each of the four keys ...
2
votes
1answer
154 views
What is the strength of unpadded RSA?
I would like to use unpadded RSA for homomorphic encryption in a toy P2P game, for things like fair coin flips and shuffling.
How many bits of security does unpadded RSA have, in relation to its key ...
0
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0answers
52 views
User data encrypt/decrypt [closed]
I was wondering which is the best way to encrypt and decrypt user data, to make it much more secure as it is possible?
I was reading about AES but i would like to know if is really the best way.
Me ...
4
votes
1answer
330 views
Why is CBC with predictable IV considered insecure against CPA
I just learned that using CBC encryption with an IV which is predictable is not secure.
From what I understand, using certain plain texts, and then guessing the IV that is uses, the attacker can ...
2
votes
2answers
684 views
FIPS 140-2 Compliant Algorithms
Is there any reference to check the list of encryption & signing algorithms which are compliant to FIPS 140-2. After an exhaustive search I could find only "AES".
Any suggestions would be much ...
4
votes
1answer
403 views
How does order-preserving encryption work?
Order-preserving encryption (OPE) is, apparently, a method of encrypting data so that it's possible to make efficient inequality comparisons on the encrypted items without decrypting them.
I've been ...
4
votes
1answer
78 views
Dimension of Encryption of a linearly dependent set of plaintexts
Suppose I have an encryption scheme of the form $ E(P)=C $ where $P$ is the plaintext and belongs in $\{0,1\}^N$, $C$ the ciphertext which belongs to $\{0,1\}^M$ and the encryption is performed under ...
2
votes
2answers
203 views
Encryption scheme with equivalent keys?
I've long been looking for a symmetric encryption scheme (or algorithm) with equivalent keys. Let me define what I want:
Symmetric encryption algorithm with encryption function $E_k$ and inverse ...
8
votes
2answers
470 views
Why RSA can't handle numbers above 76?
I'm going to encrypt the characters Zhu, and decrypt them using RSA. I'm using the public key $\{e, n\}$ and private key $\{d, n\}$. The values of $e$, $d$ and $p$ ...
1
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1answer
1k views
How to decrypt AES in CBC
i am having problems understanding how CBC works! I know that it is a chain and the IV is XORed with the PT but then what? I mean we encrypt it with key k and the result is the CT which we use for the ...
