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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Is there an efficient way to hide the encrypted plaintext length with a block cipher?

In block cipher modes of operation for encryption on input of a plaintext of $N$ blocks (We assume that the input size is always a multiple of the blockcipher mode: $N·16$ bytes) the size of the ...
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Does the MixColumns step come before or after AddRoundKey in AES decryption?

I found these images depicting the AES decryption process: In the first image, the MixColumns step comes before the AddRoundKey step, while in the second image, the AddRoundKey will come before ...
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Simple way to extend AES to 256-bit block size

What is the best way to use standard AES with a 128-bit block size to act as a 256-bit block cipher? I am aware of CMC and EME which seem to serve this purpose, but they seem to be more complicated ...
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Cryptography — with a semi-priveleged user in the middle — to prevent request-tampering with another server

I'm working on a chat server for a mobile app I am writing. I would like to use a different application server for non-chat related operations and another application for chat operations. I would ...
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51 views

1-1 trapdoor function mapping the set of $n$-bit numbers to themselves

I am looking for a trapdoor one-to-one function $f : \{0,1\}^n \rightarrow \{0,1\}^n$ (that is, mapping the set of $n$ bit numbers 1-1 onto itself [any $n$ is OK]). I was considering the use of ...
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Pohlig-Hellman exponentiation block cipher

Let $G$ be a group of order $n$ and let $e,d$ be integers such that $ed\equiv 1 \pmod{n}$. Then the exponentiation maps $x \mapsto x^e$ and $y \mapsto y^d$ are inverse maps on $G$. These maps give us ...
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How to perform benchmark of block/stream ciphers?

I would like to perform some benchmarking of different block and stream ciphers for general data (lossless and lossy data) encryption and decryption (with focus on power consumption). To get general ...
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Is there a theoretical maximum useful keysize given the block-size?

Consider a block-cipher $F$ with a $N$-bit block-size and a $M$-bit key-size. That is, if $k$ is a $M$-bit key, $p$ is a $N$-bit block of plain-text and $c$ is a $N$-bit block of cipher-text, then: ...
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Properties of Ideal Straight P-Boxes

What properties should an ideal straight P-Box exhibit?
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Ciphertext-only attack on Simplified DES

Is it possible to deduce the plaintext block or the key, given only a Simplified-DES ciphertext block (e.g. c=01110110)? I'm reading Cryptography And Network Security, by William Stallings and I'm bit ...
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How to secure a mental poker protocol? [closed]

I would like to implement a mental poker protocol in a secure fashion. How should I go about that without (preferably) infringing on the Mental Poker Framework patent?
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Can AES decrypt with a wrong key?

The title is asking the question in layman terms, but what I really mean to ask is this: Let $x \in \lbrace 0,1 \rbrace^{128}$ (an arbitrary input block) and let $K \in \lbrace 0, 1 \rbrace^{128}$ ...
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Is AES a linear hash?

So, having read a variety of documentations on AES encryption, I came to the unknowledgeable conclusion that the key schedule applied to the array of chunks, and not just the 14 cycles on a single ...
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Block cipher encryption of decryption with the same key

With block chipers can I assume that Enc(k,Dec(k,m))=m Meaning if I decrypt something with a key k and then encrypt the result with the same key k, do I get what ...
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Block Cipher vs Stream Cipher in Web Application [closed]

I'm doing research about "Cryptographic attack methods in Web Application" so I have some questions to ask you guys: Block Cipher vs Stream Cipher, which is more common used in Web Application? How ...
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Pseudo Random Generator with fixed Hamming Weight [closed]

I'm searching for way to generate secure pseudo random sequence with a fixed Hamming weight using a seed. I found below code but I need a seed to generate a sequence ... (and need know if is possible ...
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363 views

File Encryption/Decryption in ECB mode [duplicate]

Possible Duplicate: Removing Padded Value in Decrypted Message I tried to encrypt and decrypt a file in ECB mode using AES Algorithm but I encountered one problem during decryption, I don't ...
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Why is there a strong distinction between stream and block ciphers? [duplicate]

If I don't err, in the literature a stream cipher is one in which each plaintext bit is processed individually, commonly via xor-ing with one bit of a random or pseudo-random bit stream, while a block ...
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