107k 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?
31k 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 ...
997 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?
884 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 ...
265 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 ...
5k 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 ...
670 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 ...
90 views

### Why BouncyCastleAesCbcBytesEncryptor is using a salt and an initialization vector?

I'm using the class BouncyCastleAesCbcBytesEncryptor from Spring Security. One of the constructor has the following signature: ...
1k 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 ...
96 views

### Best practices for IV generation

What are the best practices for IV generation for AES and other algorithms? Is RNG enough? What if I cannot use RNG and need to use a variable that is related to some characteristic of the ...
I understood the XOR trick that allows an attacker to guess a block of a previously sent message from the client to the server: the attacker forces the client to send the message $\tilde{m} = c_n \... 1answer 1k views ### Is it safe to AES-CBC and AES-CMAC both using the same key? There is a very similar question (Using a derived key for CMAC) but it doesn't quite answer this one (at least for me it does not). I have a situation where I need to transfer some data. My data has ... 2answers 131 views ### using different IV and SALT with AES-CBC but same KEY I'm working on this project where a client can send a message, now obviously sending it in plainText is not very smart. So I decided to Encrypt it with AES-CBC. Now, each time I encrypt something, ... 1answer 557 views ### Plaintext block chaining, bad idea why? Ahead of the question, little warning. Question is not about what are the better options. Question is why it is bad idea? Ok, suppose we have plaintext$p$, which divided into blocks:$p_1,p_2,p_3,......
Let's assume that for encryption with AES in CBC mode we have $IV\in \{0\}^{113}||\{0,1\}^{15}$. I know that if we can predict next IV with 100% probability there is attack that completely breaks ...