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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1k views
How does one implement the Inverse of AES' MixColumns
I got an answer in the related question about Mixcolumn for encryption, but how about decryption?
what will I do?
Because it said that I will used this:
During decryption the Mix Column the ...
0
votes
0answers
102 views
Search tool to identify which algorithm is in use [closed]
I'm trying to identify what algorithm is encrypting / encoding / hashing passwords in a client system. I have samples of matching plaintext and ciphertext. Is there a search engine somewhere that will ...
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3answers
434 views
Which attacks can be avoided by the use of OFB instead of ECB?
For a file encryption program, I was told to use Output Feedback mode (OFB) instead of ECB (Electronic code book) mode.
Which attacks can I avoid by this choice?
5
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4answers
362 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 ...
11
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6answers
354 views
Can I encrypt user input in a way I can't decrypt it for a certain period of time?
I run a baseball league and would like to do silent auctions for free agents. This would require teams to enter their highest bid and the highest bidder at the end of the auction period would win. ...
5
votes
2answers
300 views
Practical necessity of semantic security under chosen plain text attack (CPA) in CBC mode
I was not able to understand why we practically need a CPA security in Cipher Block Chaining. (which insist on having a random IV), let say if the encryption is not CPA secure i.e , the adversary can ...
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3answers
205 views
Comparison: complexity measures vs. security
Assume that you want to compare several cryptographic primitives (say, encryption schemes), and choose one. You need to consider several complexity measures, such as the key length, encryption time, ...
3
votes
1answer
329 views
Advanced Encryption Standard Algorithm Secret Key
just a follow up question with this question..
How does the key schedule of Rijndael looks for keysizes other than 128 bit?
A 256-bit key can still encrypt a block of plaintext in 128 bit?
but in ...
2
votes
1answer
260 views
How does Output Feedback mode use the initialization vector?
How can I process Initialization Vector inside the Block Cipher Encryption box (using for example AES) together with the Key?
Will I encrypt the Initialization Vector like a block of plaintext?
So ...
3
votes
3answers
819 views
How does the key schedule of Rijndael looks for keysizes other than 128 bit?
It said in Wikipedia that:
[....] Rijndael can be specified with block and key sizes in any multiple of 32 bits, with a minimum of 128 bits. The blocksize has a maximum of 256 bits, but the ...
1
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1answer
913 views
Cipher Feedback Mode
I can't understand what CFB really is. It said in Wikipedia that CFB is same as CBC, but I find that CFB is more difficult than CBC.
Can someone explain to me how CFB works. Such as how ...
5
votes
1answer
254 views
CBC key lifetime, or, “how big is too big?”
IPSec recommends rekeying SA's figuring in both time and amount of data sent. Even when using AES-256 in CBC mode, the key and IV commonly get re-negotiated after 100MB.
My case isn't using IPSec, ...
-3
votes
1answer
424 views
Advantages of each encryption mode [closed]
What is the advantages of each encryption mode to other encryption mode..
for example what are advantages of CBC to PCBC, CBC to CFB
just like that.
so that I can filter what would be the best ...
2
votes
1answer
426 views
How to sign a message using RSA?
Assuming I already have a D, P, Q, etc of an RSA key: How do I now sign a message? If it matters – the message is around 100 bits.
I don't know much about cryptography, but I can get these numbers ...
1
vote
2answers
724 views
How to perform file encryption using 128-Bit AES?
I am confused, how can I encrypt a file using 128 Bit Advanced Encryption Standard?
Do I need only to encrypt the file name and it's content or is there something that I need to do to encrypt it? Is ...
3
votes
1answer
322 views
Does the Biclique attack on AES pose a credible risk to its security?
I have heard a lot about the biclique cryptanalysis research on AES, which as far as I know is the closest anyone has got to breaking AES.
Exactly how close did they get? Does this attack propose a ...
1
vote
1answer
107 views
Tips on conceiving safe software messaging platform
I have a personal project in mind in which I plan to use cryptography in order to let the users be confident in the fact that, even if all data get's stolen, it would be virtually impossible to crack ...
2
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2answers
701 views
How can I do a brute force (ciphertext only) attack on an CBC-encrypted message?
Given a CBC ciphertext and IV, how can I find the encryption key?
We are limited with an 8 chars key, each char in the range of [a..h], so I can generate every possible key (these are only $8^8 = ...
3
votes
2answers
287 views
Can RSA encryption produce collisions?
In RSA, a message is encrypted by $m^e \pmod N$. $N$ is the modulus, $m$ is the message and $e$ is the public exponent. (I know that $m$ should not be greater than $N$.)
My question is, can $m^e$ be ...
2
votes
2answers
253 views
Simple xor cipher extension
Probably the simplest cipher is the xor cipher with a single integer. One can extend this to use more than one integer by several means. I'm wondering if there is any benefit to doing more than this:
...
1
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1answer
652 views
Big-O Notation: Encryption Algorithms
I am currently completing a dissertation concerning the encryption of data through a variety of cryptographic algorithms.
I have spent much time reading journals and papers but as yet have been ...
1
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2answers
175 views
One-way function and factoring
I am confused about the hardness of the one-way function behind cryptography -- if someone could factor the large number produced back into two primes quickly then the one-way function would be ...
2
votes
1answer
577 views
What is the difference between CBC and GCM mode?
I am trying to learn more about GCM mode and how it differs between CBC. I already know that GCM provides a MAC which is used for message authentication. From what I have read, and seen code ...
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votes
3answers
303 views
Crypto-Compression Algorithms?
I was wondering, whether there exist such algorithms/enciphering procedures which both compress and encrypt the input data. That means, for starters, the output will be both smaller in size and ...
3
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3answers
566 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 ...
5
votes
3answers
428 views
Encryption algorithm that produces dummy output on incorrect passwords
Background:
I've been thinking about using encryption in the context of backing up files to untrusted locations (to the point of making the file publicly and widely distributed for practically ...
3
votes
2answers
7k views
How secure is AES-256?
The cipher AES-256 is used among other places in TSL/SSL across the Internet. It's considered among the top ciphers.
In theory it's not crackable since the combinations of keys are massive.
Although ...
5
votes
1answer
192 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". ...
1
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1answer
146 views
Which encodings have |encoding key| >> |decoding key|?
I'm looking for an encoding scheme that requires a very large encoding key E (>10MB) and suffices with a relatively small decoding key ...
6
votes
4answers
485 views
Is compressing data prior to encryption necessary to reduce plaintext redundancy?
As explained in William Stallings' Book, in PGP encryption is done after compression, since it reduces redundancy.
I couldn't relate encryption strength with redundancy. Could anyone explain more on ...
2
votes
1answer
78 views
Educational videos for security topics [closed]
Is there anything like the famous "sorting out sorting" video in cryptography/security.
I am looking for some nice videos that explaines SSL, SET, IPSec, PGP, S/MIME ....
4
votes
2answers
356 views
Order Preserving Encryption for Numeric Data Values
How can I ensure order of encrypted data i.e., Enc(m1) < Enc(m2) where m1 < m2, and all messages are integer values.
I have gone through Order Preserving ...
4
votes
1answer
107 views
If plaintext is random, how does it affect my choice of encryption algorithm?
I want to encrypt a key file, which is assumed to be truly random (generated with hardware RNG, for instance). Given that there are no patterns in the plaintext, what implications are there for my ...
3
votes
3answers
4k views
RSA encryption with private key and decryption with a public key
Does the encryption with a private key and decryption with a public key works in RSA? Is it done when we use RSA for sender authentication ?
Thanks.
4
votes
1answer
185 views
Why does RSA give better security on longer messages?
I am trying to understand the notion of RSA security.
Choosing a public exponent where $e = 3$ facilitates the calculations, considering that it is secure if the plaintext or message is long.
If the ...
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0answers
46 views
Elliptic curve Cryptography [duplicate]
Possible Duplicate:
Can we use elliptic curve cryptography in wireless sensors?
How to map message character to point lies on Elliptic Curve? how to ecc used in wireless sensor networks? ...
2
votes
0answers
528 views
MD5 encryption in Windows batch script [closed]
I am making a script in Windows batch to have a registration and login system that stores the passwords in a SQL database using SQLite. I need a command line MD5 encryption program to encrypt the ...
9
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1answer
1k views
Why do we use encrypt-decrypt-encrypt (EDE) in 3DES, rather than encrypting three times?
I'm wondering why we use encrypt-decrypt-encrypt sequence in 3DES with three keys instead of three times encryption with three different keys?
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8answers
460 views
Does a public key absolutely need to be used to initiate an encrypted session?
I am a software developer working on an application with the .NET platform. This application needs to provide a secure connection and encrypt all data between the client and the server. It is a ...
1
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2answers
187 views
Seeking special-use fingerprinting/hashing algorithm
For a project I wonder if there exists some kind of fixed-size checksumming/fingerprinting function in which based on this fingerprint given data block 1, it is easy to generate more data blocks that ...
0
votes
1answer
375 views
What are open problems in cryptography? [closed]
I would be starting groundwork for my thesis in cryptography , I would like to know what are current open problems in cryptography, few I know of are
Fully Homomorphic Encryption
Functional ...
8
votes
3answers
446 views
What is the best way to put a backdoor in an encryption system?
How can you put a backdoor into an encryption algorithm? Are there any techniques that can be used to reduce the time it takes to break a key?
I am looking for practical examples encryption schemes ...
2
votes
1answer
605 views
Sending KCV (key check value) with cipher text
I was wondering why it is not more common to send the KCV of a secret key together with the cipher text. I see many systems that send cipher text and properly prepend the IV to e.g. a CBC mode ...
3
votes
1answer
178 views
How can one share information using the 'host-proof' paradigm?
I am attempting to make a web-based secure password management and sharing utility, both as an academic exercise and to fully understand and feel safe about using it.
I really like the idea of a ...
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2answers
133 views
How can I store a combination of multiple pass phrases?
Let's assume we have 2 phrases, one is the real password from a user, and the other is generated from the real password and almost impossible to guess. You would need both to authenticate a user. What ...
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0answers
109 views
What will be the way to go about deciphering this kind of cipher? [closed]
I've come across this cipher and have tried unsuccesfully to decipher it.
http://codepad.org/aea7Wuyl
The only 'hint' that I have gotten so far as to how I am supposed to crack it is the word ...
1
vote
2answers
273 views
Passwords with same SALT. What does this mean?
If the same SALT is used for many passwords on a Linux server, in what way is that a security risk?
Does the mean, that a user (which can change his own password) can calculate other users passwords?
...
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1answer
629 views
How does PBKDF1 work?
I need some basic guideline on Password Based Key Derivation Function. PBKDF1 generates a key from password and salt using Hashing algorithm (like SHA1, SHA256, MD5).
What is the step behind this?
2
votes
1answer
903 views
Secure way to transfer data over NFC?
I am currently writing a payment system to accept payment details from an NFC enabled smartphone (BlackBerry 9900) to a Windows client (C#.NET)
I am currently having two issues relating to security:
...
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0answers
99 views
Does anyone know which encryption scheme produces the following output? [closed]
My company is using software that stores an encrypted database password in a publicly accessible file. The encrypted version looks like this:
...
