AES (Advanced Encryption Standard) is a symmetrical block-cipher algorithm with a 128-bit block size, and key sizes of 128, 192 or 256 bits.

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Is double AES-CBC encryption with the same key and IV unsafe?

If some plaintext encrypted twice with the same AES function (CBC-mode), same IV and same key, is it possible to retrieve either the key or the plaintext?
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Deoxys: disadvantages vs. AES?

The CAESAR candidate Deoxys is based on a tweakable block cipher that seems to be a strict improvement over AES, in that it is a tweakable cipher resistant to related-key attack. The mode proposed ...
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Symmetric cipher speed (AES vs Camellia vs Twofish)

If I have understand correct, Twofish is more secure (harder to break) than AES and Camellia, but Twofish is slower than AES and Camellia. But how can I mesure the speed difference between AES vs ...
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What would happen to AES if we replaced MixColumns with ShiftColumns?

I have this as a question in an assignment and I guess I don't fully understand the steps. I understand that if we omit MixColumns, then every byte of the ...
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61 views

How is decryption done in AES CTR mode?

Since AES CTR mode uses a unique IV and counter to produce the key to XOR with the plain text to get the ciphertext, the question is so as to how decryption is done. Since AES CTR produces a ...
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96 views

Is this cascading encryption, and is my security weakened as a result?

I'm trying to understand what is, and what is not, considered cascading encryption. All of the posts and conversations I've read over the past few days discourage the practice, including this article. ...
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64 views

How secure is the OTR protocol?

I am using Adium and wondering how secure it is. I believe it uses AES-256 (I do not understand what that means) by default. It also requests that users exchange fingerprints with each other before ...
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138 views

Length of encryption password aes-256-cbc

I'm encrypting a file with sensitive information with cat secret | openssl aes-256-cbc -a -salt > secret.enc I am choosing a random encryption password with <...
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How to use OpenSSL command line utility to encrypt data with encrypted key from public key?

I may not be asking the right question. I am fairly new to data encryption. I am currently being sent encrypted data that's stored as follows: [ [keysize] [key encrypted with public key] [ivsize] [...
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Do you need a HMAC if decryption attempts are severely limited?

I am considering an application where data bandwidth is extremely limited, and considering removing message authentication codes from encrypted transmissions. The encryption method is currently AES-...
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73 views

SHA256(RsaPrivateKey) == AES key?

I have an RSA private key (more specifically, an SSH key in Putty format, 4096bit) and want to use its SHA256 hash as an AES256 key, instead of using an independent newly generated AES key. Are ...
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Parallel file encryption and authentication for large files

For a cloud storage upload client I want to encrypt files during upload, so that they cannot be read by the cloud service provider or anyone who gains access to the account. I would like to use some ...
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350 views

What is the fastest block cipher in the (Intel) world?

In AES competition,Rijndael cipher obtained first rank and become Standard and Serpent, Twofish, RC6 and MARS obtained another ranks and I know that Serpent took second rank because it was slower than ...
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GCM: use the same key:IV pair to encrypt file and filename

Using Java, I wrote a piece of code that encrypts a given file with AES in GCM mode of operation. So far nothing uncommon. Now I would also like to encrypt the filename, in the following way: ...
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Deriving AES key and HMAC key from shorter master key

I am working in .NET and as far as I can tell the only choice for key derivation is PBKDF2-HMAC-SHA1. SHA1's output size is only 160 bits. But I am implementing authenticated encryption and thus ...
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Deriving 256-bit key from PBKDF2-SHA1

I am working in .NET and their PBKDF2 only uses SHA-1. I am using it to, given a user-supplied password and random salt, generate a 256-bit AES key. The plaintext is encrypted with the AES key and ...
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108 views

How to Perform Computation on AES Encrypted Data

I have this code that successfully performs symmetric encryption using AES algorithm. How can I go about performing computation on it to achieve somewhat homomorphic encryption? ...
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550 views

Why can't we use the first block of AES-CBC as MAC

As per topic, why can't we use the first block as MAC instead of using the last block? what's the rationale?
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Stripping off message authentication or signature

If attackers can strip off RSA / EC / -DSA digital signature and conduct CCA on AES-CTR or CBC payload, why can't they do the same for AES-GCM?
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How to use AES-CBC to password-encrypt a small block of stored data

I have a small block of data (16 bytes) that I am required to encrypt, store (in an unsecure, visible location). Later I have to retrieve and decrypt it. I must use AES-CBC and a user-entered ...
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58 views

AES encryption time difference for same data [duplicate]

When encrypting same data with AES, encryption time for the first encryption is longer than the second one. In the same program, I have written encrypt() function ...
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Is OCB the state of the art in authenticated encryption modes of operation for block ciphers?

OCB mode seems to represent the state of the art in authenticated encryption modes, largely due to its speed – it is faster than GCM even when GCM has hardware support. Its only drawbacks seem ...
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How does Microsoft's BitLocker Recovery Code work?

I don't trust Microsoft BitLocker because it is closed source, which makes it so people can't audit it. But now I'm really interested in how its recovery code works. In my own knowledge, encrypted ...
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Is there a key for AES-128, 256 etc, where cleartext equals ciphertext? [duplicate]

Is there a key for AES-128, 256 etc, where cleartext equals ciphertext? (regardless of modes like chaining or ctr-cbc)
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Using AES-CTR to generate AES subkeys from a master key and nonce

Suppose I would like to encrypt some data using AES-GCM because it has hardware support on my processor and it is secure. Unfortunately, I don't like the 96-bit nonce size, because I want to randomly ...
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Can we use more than one irreducible polynomial in AES?

I understand that the irr. poly is used to form the s-box (and inv. s-box), the key schedule and the mix columns. But could we use a different irr. poly for the mix columns and another for the key ...
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Why is the permutation in AES (and other ciphers) not random or key-dependent?

If the permutation in AES (or other ciphers) were randomly generated or dependent on the key, would it not be stronger against differential attacks? If this is so, then might we need fewer rounds for ...
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Nonce encryption with Poly1305-Chacha20

I have seen that a couple of companies (like Google, Apple HomeKit) are adding "ChaCha20-Poly1305" as an encryption option. Poly1305 requires algorithm to encrypt the nonce. The Poly1305-AES ...
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Schnorr signature security level as compared to AES/RSA

As per the Schnorr's original paper (1991), The Security Complexity $2^t$: We wish to choose the parameters $p$, $q$ so that forging a signature or an authentication requires about $2^t$ steps by ...
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Disk encryption using AES-CBC: is reliance on previous block data a downside?

I have seen drives that boast that they use AES with CBC mode, which doesn't really make sense in my opinion, sure it's more secure than ECB (but actually, leaving security aside, ECB is better suited ...
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Brute force knowing a part of the password

So here is the problem, my brother forgot about the eight digit numeric part of his password, he is using Ubuntu 15.04 default whole disk encryption To make it clear, this was his password (example) ...
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390 views

Does the SHA-256 sum of a 256-bit key help you crack it?

If I have the SHA-256 sum of a 256-bit AES key, can I determine the key any faster than if I merely had a ciphertext and the corresponding plaintext?
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Is it possible to utilize an AES-128 encryption hardware unit for AES-256?

There exist processors (for example ARM v8/v9 archicteture based), which cannot do AES-256 hardware based, but are equipped with AES-128 encryption hardware units. Is it possible to utilize an AES-...
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Encrypt-then-HMAC implementation - am I doing it right?

I want to implement authenticated encryption using C#. There is a dot net class called encryptAndAuthenticate, but it is only supported on windows 8 or later, and I need the code to also work on ...
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How secure is $\operatorname{AES256}_{\operatorname{ECB}}(\operatorname{ChaCha20}(\text{plaintext}))$?

Suppose I encrypt a bytestream using ChaCha20, and then encrypt the resulting ciphertext using AES in ECB mode. How secure is the combination?
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Is parallel, vectorized NORX nearly as fast as hardware-accelerated AES-GCM?

As I understand it, NORX gets 3.5 CPB in an unoptimized implementation. But NORX can be parallelized. With 4-way SIMD, I would expect about 7/8 CPB performance. This is nearly as good as AES-GCM in ...
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AES - Size of T-Boxes and obtaining T-Box values

In article "A high performance ST-Box based unified AES encryption/decryption architecture on FPGA" (http://www.sciencedirect.com/science/article/pii/S0141933115001945) two 32Kb dual-port BRAMs are ...
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How does the split mask countermeasure work on AES?

I am trying to understand the split mask countermeasure which is a masking method to avoid side channel attacks. Let's first describe the principle and then try to apply it to AES. I found this paper ...
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Is webkey a reasonably secure authentication system?

I just created Webkey in the last couple days. This should allow any website to do single-password auth with a much higher level of auth security and convenience for users (single password with ...
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For what does “Rcon” stand for in Rijndael/AES?

How do we expand the abbreviation โ€œRconโ€ used in the Rijndael key schedule? I know what it is, I know how it works; I just do not know for what it is a shortcut for. I mean: if "Sbox" is "...
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Why need mapping to slots to embed bytes in AES-homomorphic encryption?

The encoding of each AES bytes $๐›ผ_๐‘–$ is using CRT(Chinese remainder theorem). It means that there is an aggregate plaintext $H$ such that: $H \mod F_0 =๐›ผ_0(MappingData[0])$ $H \mod F_1 =๐›ผ_1(...
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Cloneability of AES-128

I would like to implement an anti-counterfeiting scheme for tools my company manufactures. This would ideally be done via RFID/NFC tags. However, the environment in which these tags operate would ...
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Can I open a file in plaintext (already decrypt) but the cipher doesn't change?

I want to create an app that encrypts a file and saves it to the Dropbox. Thus, I open and edit this file, I want the file is already decrypted, but the encrypted file that stored in Dropbox still in ...
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Proper authenticated encryption

I am using AES-CBC, authenticating using HMAC-SHA512 and I was wondering whether my thought process and implementation are correct. The message send over the network is: HMAC(64Bytes),IV(16Bytes),...
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What is considered a “weak key” in AES?

I need to construct an AES key from an array of bytes (in Java), but I first I have to check if the key created from these bytes would be weak. Java can check for weakness for DES, but not for AES. ...
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Sodium crypto_aead_aes256gcm_encrypt ciphertext length > plaintext length

Using the crypto_aead_aes256gcm functions from Sodium produces a ciphertext of "at most mlen (plaintext length) + crypto_aead_aes256gcm_ABYTES bytes (16 bytes) are put into c (ciphertext), and the ...
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Is regular CTR mode vulnerable to any attacks?

Regular plain CTR mode, is it vulnerable to any attack? I plan to write a program to encrypt a drive with ctr mode. Would this be wise? Would AES be better? When I look at this diagram, it looks ...
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Decrypting a file encrypted with AESCRYPT using key instead of password

i have encrypted a file using aescrypt and took memory image while the file was being encrypted and hence have the key that was used for encryption in the image but not the password, can i decrypt the ...
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I am trying to understand how AES works

I am trying to understand how AES encryption operates. I am trying to run through the steps on paper to understand. So far, I am creating a simple example. I have the plain text "MESSAGE TESTTEXT" ...
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How secure is a client-side javascript encrypter?

A friend of mine needed help with her website and asked how to send me her login information securely. I've never known how to do this, so I figured now was the time to learn. After some googling, I ...