Linked Questions
26 questions linked to/from Why is CBC with predictable IV considered insecure against chosen-plaintext attack?
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2answers
94 views
Randomly initialised global counter used to encrypt the kth message with $\operatorname{IV} = \operatorname{IV} + k \hspace{5mm} mod \hspace{5mm} 2^n$ [duplicate]
The use of an increasing IV is not secure for a block cipher. That is, using a random IV for the first message then $\operatorname{IV} + 1$ for the second , $\operatorname{IV}+ 2$ for the 3rd etc. How ...
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vote
0answers
95 views
AES CBC Initialization vector - Security issues [duplicate]
I have 2 questions regarding security issues related to initialization vectors used in AES CBC
Consider that I'm using a sequence number (which increments with every encryption) as an initialization ...
80
votes
9answers
119k views
Should I use ECB or CBC encryption mode for my block cipher?
Can someone tell me which mode out of ECB and CBC is better, and how to decide which mode to use? Are there any other modes which are better?
31
votes
2answers
8k views
7zip : Why does encrypting the same file with AES-256 not give the same output?
Using 7-zip 19.00, on Windows 10 1909, build 18363.592, I encrypted a text file with the contents "hello there" using AES-256 and the password "123". I did this two times, the exact same procedure, ...
22
votes
3answers
34k views
How can Cipher Block Chaining (CBC) in SSL be attacked?
I am trying to understand how CBC-mode in SSL/TLS can be attacked.
I have been looking around online but all examples and explanations are very hard to understand and follow. Can you give a simple ...
10
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1answer
1k views
Which block cipher parameters should be kept secret?
Which of the parameters of a block cipher (e.g., algorithm name, mode of operation, IV (if any), key length) are essential to keep secret?
4
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1answer
7k views
CBC with a fixed or random IV
I have three questions related to the use of IV within CBC mode of operation:
Why, exactly, is it so bad to have a fixed (or predictable) IV in CBC mode? An example would be great!
Given 1., why is a ...
8
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2answers
1k views
CBC variant: why encrypt the nonce with a different key?
I am a newbie at cryptography. I understand the CBC encryption, somewhat. You don't want to use the same "IV" for every message because then the ciphers are not very random. My question is regarding ...
7
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1answer
284 views
Predictable, but private IV in CBC
It is said that a predictable IV is dangerous, because you can do adaptive chosen plaintext attacks. But if the IV is never seen to the attacker, is it still dangerous? What I mean, is that the IV is ...
2
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1answer
1k views
Is it safe to AES-CBC and AES-CMAC both using the same key?
There is a very similar question (Using a derived key for CMAC) but it doesn't quite answer this one (at least for me it does not).
I have a situation where I need to transfer some data. My data has ...
3
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2answers
2k views
How to defend AES against chosen-plaintext attack?
I have a server which encrypts files with the same AES key. Users can upload a file and download its encrypted version. A user can upload as many files as he wants. Users can decrypt the documents via ...
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vote
1answer
1k views
Question about IV/initialization vectors
I found some code to get crypto-js to encrypt data in the browser, and with a pointer from someone on SO, it now decodes data as well.
My next question is about the use of an IV; is an IV like a salt ...
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2answers
96 views
Is CTR more secure than CBC?
In cryptography, a block cipher mode of operation is an algorithm that uses a block cipher to provide information security such as confidentiality or authenticity. A block cipher by itself is only ...
2
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2answers
557 views
using different IV and SALT with AES-CBC but same KEY
I'm working on this project where a client can send a message, now obviously sending it in plainText is not very smart. So I decided to Encrypt it with AES-CBC.
Now, each time I encrypt something, ...
4
votes
1answer
737 views
Fixed-prefix IV in CBC mode
I know the Initialization Vector needs to be unpredictable. Does it apply to the IV as a whole, or to every bit in the IV?
I have multiple devices with poor entropy sharing the same key and I want to ...