Encryption is the process of transforming plaintext using a cipher to make it unreadable to anyone except those possessing the key.
3
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1answer
148 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
115 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
185 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
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1answer
142 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
226 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
117 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 ...
-2
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1answer
119 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
355 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
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2answers
175 views
Two step encryption
Is there any asymmetric cryptography algorithm which will allow recursive encryption.
...
4
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1answer
143 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
120 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
108 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
2answers
126 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 ...
4
votes
5answers
320 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
147 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
1k 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 ...
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1answer
156 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
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1answer
234 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
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
votes
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 ...
1
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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 ...
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 ...
0
votes
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
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 ...
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
321 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 ...
1
vote
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 ...
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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 $n$ ...
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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
280 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
191 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 ...
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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 ...
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1answer
91 views
Matrix Multiplication of Bits
How to multiply the matrix of bits
example I have two 4x4 matrices of bits
...
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
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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
vote
1answer
292 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
126 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
votes
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
326 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
votes
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, ...
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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 ...
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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
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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 ...
