A block cipher is an encryption algorithm which encrypts fixed-size blocks of plaintext to same-sized blocks of ciphertext. For good ciphers every bit of the ciphertext block depends on every bit of the plaintext block and every bit of the key.

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How AES treat string input to encrypt data and what will happen if the cipher key is less than that expected?

The official docs of AES have several example of how hexadecimal or byte input can be encrypted. I have some problem about the input text and cipher key. My question is: How can encrypt string input ...
2
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105 views

Can CFB mode of block cipher be used as a commutative encryption?

Can CFB mode of block cipher be used as a commutative encryption? Is it possible to use CFB mode of AES block cipher to create commutative encryption? With CTR it is possible but not secure.
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Is this commutative encryption protocol secure?

My assumptions are: encryption must be commutative man-in-the-middle is not an issue I would like to implement the following scheme between 2 parties ($A$ and $B$) to exchange a key: Lets $C = P ...
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One cipher to rule them all?

I learned from Dan Boneh's course that many cryptographic primitives (prngs, stream ciphers, hashes, hmac, key derivation functions) can be built from just one a block cipher or PRF. For example, the ...
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Reasons for components of AES

I started reading "Cryptography: theory and practice" by Stinson, and I am trying to understand the reason behind the choices for the different components of AES since they seem quite arbitrary. In ...
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Does XTS provide random write access?

I'm trying to find a sufficient encryption mode that supports random read and write access. It seems like XTS is a perfect fit, since in my use case authentication and integrity insurance are handled ...
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Double the key in block cipher - which approach is better?

Assume than you have a block cipher $E(k,m)$ for which the only attack exists has complexity of $2^{64}$. You consider to double the key size by either: $E'_1(k_1,k_2) := k_1 \oplus E(k_2,m)$ $E'_2(...
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Block Ciphers - Standardize plain text

I need to use AES-128 to encrypt a plain text about 720 bits. Is it correct to say that – in this case – the plain text will be divided in 5 blocks of 128, the result will be equal 640 bits, and the ...