Questions tagged [initialization-vector]

Unique data used by block cipher modes of operation to randomize the output in order to achieve semantic security. Also for other similar constructs in other iterative algorithms.

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How to generate initial vectors during DPA attack on stream cipher in real life?

I was trying to understand the procedure of the DPA attack on Stream cipher (like Mickey-128). I learned that, the attacker need to build hypothetical power consumption matrix with different initial ...
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LibTomCrypt Documentation on LRW Mode/Tweakable Block Cipher - Apparent Contradiction?

In the LRW mode discussion on page 34/161 of the LibTomCrypt manual, available here for example https://opensource.apple.com/source/CommonCrypto/CommonCrypto-55010/Source/libtomcrypt/doc/...
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Is it okay to have no IV when using AES-CBC with unique keys, that are however derived from one shared key?

Given $\operatorname{AES-CBC}$ (128-bit), with $IV=0$ and unique encryption keys $$K_{Enc} = \operatorname{CMAC}(MK, \text{known_text})$$ where $MK$ is a shared symmetric 128-bit key and $\text{...
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Seekable cipher, is AES CTR a good solution?

I'd like to create a simple file-cipher, which provides seekable encryption (so I can decrypt any part of the encrypted message, without the need of decrypt from the start). Here's my current idea: I ...
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Rijndael - is there some difference in resistance between counter in generator input and in IV?

I am thinking about Rijndael implementation in order to store tokens (cannot be hashed) - one token for one user. And finally I get stuck with key/IV generation problem :( The questions are: 1) Is ...
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1k views

Keepass Twofish plugin security

Keepass is a well known open-source password manager program, with plugin support. One of the offered plugin is a twofish encryption mode of operation in lieu of the build-in AES algorithm (http://...
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How can I decrypt AES-256 GCM with key with a IV that is missing?

I want to decrypt a file that has been encrypted using AES-256 in GCM mode in libressl. I have the key but I don't have the IV, is there any way I can still decrypt?
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Proving Security of a Tweakable Block Cipher in CBC Mode (Threefish)

I want to prove the security of a Tweakable Block Cipher in CBC Mode How does one prove the security of a Tweakable block cipher (ie Threefish) in CBC mode with a random IV and a constant (public) ...
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Changing a bit in IV of MD5

It is obvious that changing even one bit in data or IV (initialization vector) will change the hash value a lot. I want to know if, for example, changing a single bit within the $IV$ in MD5 can be ...
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Can Trivium ciphertext be decrypted by an adversary if the key is known, but the IV is not?

Suppose that the adversary is able to recover the key of Trivium cipher. But the associated IV is unknown to him. Will he be able to decrypt the ciphertexts without any complexity?
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Use of Initialization Vector in a Hash Function

Why is an Initialization Vector used in a hash function? Some hash functions do not seem to need an IV, why do other hash functions need one?
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CBC mode is not IND-CCA2 secure with no prediction of IV

How can it be explained that CBC mode is not IND-CCA2 secure, in case that the IV can't be predicted by adversary. Edit: In decryption of CBC, for each block it is XORed with previous block's cipher ...
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744 views

IV and Headers inside cipher text

I am a bit confused about the use of IV, and key hash. Is the key hash and IV stored inside the headers of the cipher text? Isn't it a security risk to store this header information? By key hash I ...
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37 views

Is 64-bit SHA-256 IV-based MAC for fixed-length messages reasonably secure?

I want to use truncate8(SHA256-nopad(IV=secret, message)) as a 64-bit MAC, where message is guaranteed to be exactly one hash ...
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Do I need an inititalization vector if I don't care about message leaking?

In Safety of a private key when knowing the full content of an encrypted message in case of fixed initialization vector, an answer says using a fixed IV is bad practice since it allows statistical ...
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33 views

How to allow a partner to encrypt a message that I can decrypt without using a random initialization vector?

My company has a requirement to allow a partner vendor to log people into our web app via some kind of single sign on. We need this to be a simple process for them, not involving the use of ...
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47 views

Is it possible to encrypt a message stream with the same IV each time and for it to be secure?

I know we should ideally never reuse the IV (Depending upon the mode of encryption used), but is it possible to have a protocol which uses the same IV for the message stream and is as safe as one ...
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45 views

What is the most secure way to encrypt certain properties in logs

I would like to encrypt certain data before logging it. Currently, I use a private key and a static IV. Looking at generating a suitable IV I am concerned about the overhead in generating CSPRNG ...