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0answers
49 views

Choosing Key and IV in AES-256

I am working on a real-life project for a firm. I have to encrypt data using AES 256 as per specification. I want to know how are the key and IV are really chosen in real world projects. /dev/urandom ...
13
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5answers
2k views

Why does IV not need to be secret in AES CBC encryption?

According to Wikipedia, the initialization vector (IV) does not have to be secret, when using the CBC mode of operation. Here is the schema of CBC encryption (also from Wikipedia): What if I ...
0
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1answer
34 views

AES-CTR with PBKDF2 for IV for file archiving at server. Is this ok?

I have tried to grasp enough of encryption/hashing to be able to implement a secure storage for files, server side. Once I have it down to reasonably safe I'll go over it with an expert. There is no ...
3
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1answer
78 views

Is having a unique key to encrypt data not sufficient

Is it necessary to use a unique Initialization Vector (IV) with various cipher modes of operation (e.g. CBC) even though I use a unique key to encrypt plain text every time? It is said that an IV ...
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2answers
42 views

Could I use a TimeStamp also as IV?

For an academic application, I use AES-GCM to encrypt my frames between 2 parties. To enhance security, and reduce the possibility of replay, I'd like to use a TimeStamp in my frame exchanges. But, ...
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2answers
77 views

Is an Initialization Vector (IV) required with unique data?

When used to encrypt data that is unique, is an Initialization Vector (IV) still required? For example, Credit Card numbers or Social Security numbers. The ultimate point of an IV is to ensure that ...
6
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1answer
97 views

Using AES with same salt / IV - required for pattern matching algorithm

I need to securely encrypt data we are storing, but for each client I need the same plaintext to encrypt into the same cypher text. The reason for this is the data is still required for a pattern ...
2
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0answers
54 views

Determining time it would take to exhaust IVs on 802.11b/g/n

I'm trying to learn about WEP attacks at the moment. I know that attacks against WEP require collisions of the initialization vectors. Is there a way to determine how long it would take for the ...
5
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2answers
84 views

Two ways of generating the IV

I'm looking at some code, and in a particular scenario, the code would need to generate two IVs. The second IV-generating code simply uses the C# Rijndael GenerateIV() The first IV-generating code ...
2
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1answer
672 views

How to implement encrytion/decryption system using IV between mobile app and web service

In my app we are going to send encrypted data to the web service. I am using the following code to encrypt and decrypt the data - public class DecEn { private static final String password = "test"...
6
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3answers
8k views

Encrypting using AES-256, can I use 256 bits IV?

I want to encrypt data using AES in java, and I want to intialize the cipher with Initialisation Vector. Can I use 256-bits IV ? Or I must use only 128-bits IV ?
5
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1answer
116 views

Do IVs need to be unpredictable?

I am encrypting a sequence of messages with AES/CTR. For each sequence, I generate a random initial IV, say IV(0). Define IV(i) = MD5(IV(i - 1)) for i = 1, ..., n. Then for each message m(i), I ...
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0answers
106 views

For use with RC4 how do I combine a reused key and an initialization vector

I am an a-level student writing an encryption program using an rc4 implementation I have written myself. I have the basic algorithm coded correctly (and I have checked that some ciphertext for a given ...
0
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0answers
186 views

Cryptographic Testing

Given an algorithm (say, AES), how to create/generate test vectors? I have tried using the NIST test vectors for AES and found it to be working fine with a package of "chilkat". Suppose, for a ...
5
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2answers
902 views

Can the IV + Salt be the same?

During my encryption app i've got the password creation bit: PBEKeySpec spec = new PBEKeySpec(password.toCharArray(), salt, 10000, keyLength); and later on the actual encryption part: cipher.init(...
4
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2answers
2k views

What's the point of the nonce in CTR mode?

Does having a nonce in CTR mode actually improve security (vs. just using 1, 2, 3, etc. - basically a constant nonce of 0)? As far as I can tell, the best-case scenario security-wise is that the ...
2
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2answers
7k views

Is Salt, IV and Key necessary when encrypting password in a database using AES? If so, how should they be used?

Imagine I have a website with user accounts. I want to authenticate users, so I need to know if the password they provide matches the one stored in my database. To protect the passwords from prying ...
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1answer
159 views

How to generate Initalization Vectors correctly

I'm working on a project that splits large files into several encrypted fixed-size blocks (e.g. 4KiB). Those blocks shall be used to be stored persistently on a storage device. Blocks are encrypted ...
4
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2answers
7k views

Why would you need a salt for AES-CBS when IV is already randomly generated and stored with the encrypted data?

I was looking at this code and came across these comments which says encrypting without a salt is insecure. Why would it be insecure when you are already using a random IV for each value? I think the ...
0
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1answer
511 views

encrypting a file with an RSA key

I wrote a java program to encrypt and decrypt files using AES algorithm in CBC mode and a random initialization vector. but there is something fundamental I'm not understanding:first I generate a ...
3
votes
3answers
676 views

Is there an attack that can modify ciphertext while still allowing it to be decrypted?

Is there any way an encrypted file using AES-256 could be modified without alerting the file owner, ie., so it can still be decrypted with the same key? I know that without an initialization vector ...
4
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2answers
10k views

Using AesCryptoServiceProvider in C#, should using an incorrect IV mangle just the first block?

This question was also asked on StackOverflow, but with no answers, and I thought this may be a better exchange, since I have the same question. http://stackoverflow.com/questions/9331984/using-c-...
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2answers
4k views

Should AES always give the same output?

I'm having trouble understanding AES and would like to know if encrypting the same text with the same key two times in a row should give the same output. Is there any salt or something that would ...
8
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3answers
968 views

How do poor-quality initialization vectors affect the security of CBC mode?

(If the consensus is that this question belongs on crypto, rather than here, please feel free to [tell me to] migrate it.) From what I have read (looking specifically at AES in Cipher Block Chaining ...
2
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1answer
141 views

Is it safe to derive an IV partially from the secret data if it is hashed before use?

To help ensure uniqueness of IV's used in a CFB AES-256 cipher, software I know of gathers bits from various sources including the plaintext being enciphered, and runs that through an SHA-256 hash. ...