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Questions tagged [aes]

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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1answer
293 views

Security levels in NIST Post-quantum project: e.g. AES-128 vs SHA-256

In an article about NIST Post-quantum Standardization project I read about the security criteria of the proposed schemes and there was this table (Level I lowest security, level V highest): Level I: ...
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Finding key for AES-128-CBC knowing plaintext, ciphertext, IV, and a long list of possible keys

I have an extra credit assignment in school and I am having a lot of trouble trying to figure this one out. I'm new to cryptography and this is the first class that I've really been exposed to it. I ...
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2answers
63 views

What is the purpose of salting when integrating PBKDF2 with AES?

I'm a bit new to cryptography and I'm trying to wrap my head around PBKDF2 and AES. As a disclaimer, this is not going to be used in an actual application, I'm just testing things locally as a fun ...
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45 views

Reason for Security Level of AES

I know that a 128 bit key for AES yields a (around?) 128 bit of security. That means the best attack against the AES scheme is as strong as just brute forcing the key? What is the intuitively ...
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1answer
79 views

Are there any other highly trusted and secure symmetric encryption algorithms besides AES?

AES is the gold standard for symmetric encryption. It is highly trusted and highly secure. Do any other symmetric ciphers - besides OTP - come close to AES's usability, security, trust-ability?
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143 views

AES Diffusion at Block Level

AES provides diffusion at the block level by implementing the ShiftRows and MixColumn sublayers. The former permutes data on a byte level, wheres the latter combines blocks of four bytes. Can it ...
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1answer
52 views

How can AES-CCM behave as an AEAD stream cipher?

AESCCM- Couter with Cipher Block Chaining Message. As it uses cmac for generation for tag , which is internally aes-cbc (block cipher, need block size, may require padding) And Encryption is done ...
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3answers
383 views

AES-CBC with zero IV and a unique first block

Is it safe to generate the IV for AES-CBC as the following? It's like the real IV is all zeros. The first block of data will be a low-entropy but unique data. Once the first block is encrypted, the ...
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2answers
129 views

Is it required to use a random IV for AES-CBC with random key per message? [duplicate]

I'm developing a program to encrypt and decrypt a file with AES-256/CBC in Java. And I want it to be safe enough. In my case, I generated random AES key for each file to encrypt and decrypt them. My ...
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23 views

AES-MixColumn layer in the last round

In the "Introduction to Cryptography: With Coding Theory" by Trappe and Washington, in the chapter about AES algorithm the authors say that in the last round of the encryption algorithm the MixColumn ...
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AES - Non-linearity hinders differential cryptoanalysis

Can you explain me, in simple terms if possible (I'm not a mathematician :( ), why the non-linearity introduced by the AES s-boxes hinder the differential cryptoanalysis ?
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1answer
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Where is the authentication tag stored in file encrypted using AES-GCM?

So I am using cryptopp to encrypt a file in a project and I am using AES-GCM. I have a 256bit key and a 128bit ivec and a 128bit tag that I use to encrypt files. However, I want to know where the ...
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2answers
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Increasing number of rounds in AES

AES-128 requires 10 rounds ( AES Description, Wikipedia ) However Bruce Schneier has recommended AES-128 use 16 rounds ( Schneier on Security: New Attack on AES ) Could that be implemented as two ...
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1answer
56 views

Would adding more rounds to AES increase security?

As the title states, would increasing the rounds by doubling them to Bruce Schneiers recommendation of 16, 20, and 28 increase security? And how much? As a bit more, would increasing rounds, keys, ...
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3answers
149 views

How much would this AES modification improve security? [on hold]

How much would using AES-CTR like 3DES improve security? Like so (Using a 512-bit key split into two; $K_1$ & $K_2$, and seperate nonces for all stages): ...
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2answers
55 views

What are the actual merits of Galois/Counter Mode?

GCM (Galois/Counter Mode), in particular in combination with AES, has been a de-facto gold standard for years. Encrypt and authenticate in one step, that's just too awesome, and terms like AEAD work ...
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1answer
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Does AES encryption of a NTRU pivate key reduce security?

The NTRU crypto system requires quite long keys. For example with parameters N=439 and q=2048 the security is 128 bits and the key_size is 4829 bits. When the private key is encrypted with AES-256 ...
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0answers
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What should the hamming weights be between every iteration of AES?

I have an assignment where I have to print out the hamming weights between every iteration of AES's diffusion steps and I have been getting a maximum weight on every iteration, but I can't seem to ...
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2answers
53 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, ...
4
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1answer
409 views

What is the LENGTH parameter in EEA2?

In the EEA2 option for encryption in LTE the AES-128 algorithm is mechanized. There, the nonce used in the CTR Mode is a 128-bit value. The first 64-bits are covered by a COUNTER, a BEARER, a ...
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12 views

encrypt data in AES with mode CBC [closed]

I want to encrypt data in AES with mode CBC and in Padding PKCS7 I'm having trouble displaying encrypted text ...
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1answer
49 views

Encypt a file with AES using a secret key derived with Argon2

I would like to encrypt some sensitive files on my computer and smartphone so that they remain unreadable even if the computer is stolen. So far as I'm concerned, AES is the best encryption algorithm,...
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1answer
61 views

Which AES modes can decrypt from anywhere in the ciphertext

CTR is amenable to parallelization because you can split the message into chunks, each chunk having a range of counter values associated with it, and encrypt (or ...
2
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1answer
41 views

What value for a Rfc2898 (PKBDF2) is overkill?

I am working on a project which needs to share messages, and part of that project is deriving a password, I am currently using a value of 65537, totally arbitrary (...
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1answer
34 views

Is it safe to compute HMAC(Base64(IV) || “,” || Base64(CipherText)) instead of HMAC(IV || CipherText)?

Let || be the concatenation operator. Let CipherText = AES(Key1, IV, Message). Let us assume AES is used in CBC mode. I want ...
4
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1answer
316 views

Are there any known problems or attacks for using SHA1(AES_key) as the HMAC key?

See this answer that explains the following sequence of operations: CipherText = IV|| AES(key1,iv,message) tag = hmac(key2,ciphertext) That answer says, You ...
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5answers
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Why use complex encryption algorithms? [duplicate]

I have recently gotten interested in cryptography, so I looked some things up. I thought, why even use AES or DES or any other complex way for encrypting data when there are far simpler ways, like ...
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1answer
129 views

Whats AES-256 max input size?

Does the AES-256 encryption standart have a max input length? If not, does it mean we can even translate a book to it? Like md5 doesnt care max input length?
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1answer
82 views

Is using the same MAC twice insecure?

I was thinking last night about whether or not a HMAC-Encrypt-HMAC would be secure if you used the same HMAC key. Here is the full recipe: Compute a HMAC on the data to encrypt, and append it to the ...
3
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1answer
98 views

Why weak modes of operations are not banned?

If some modes of operations of AES are not secure (like ECB or CBC), which are prone to bit flipping / manipulation attacks, and why they haven't they been banned or advised against by NIST for other ...
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1answer
85 views

AES-128: can any two keys generate the same ciphertext from the same plaintext?

This is a purely theoretical question. I've found some similar questions, but they're not what I'm asking. Most importantly, I'm not asking whether anyone can find the hypothetical duplicate. I'm not ...
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3answers
66 views

AES Cipher Block Chaining 128 bit message

I understand that for AES CBC you need to split the plaintext up into blocks and perform XOR'ing using the previous blocks calculations etc. However, if your message is exactly 128 bits long, do you ...
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1answer
678 views

AES in OFB mode and IVs

I'm trying to understand cryptosystems and their implementations to understand how to properly implement them. I have a function implementing AES-128 in OFB mode. Let's call it ...
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0answers
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What if an AES Whitebox 1024-bit (or larger key) is created? Does it increase complexity consistently?

Following the Chow et al paper and Muir's tutorial, I was able to implement the AES algorithm using tables embedding keys of 128, 192 and 256-bit sizes, later extended to 1024, 2048 and 4096-bit sizes....
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2answers
649 views

Is it possible to identify a Serpent encryption key in memory?

It has been shown that AES keys that are in use can be identified in memory. This identification relies on discovering expected round keys in memory that are contained within the key schedule. My ...
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61 views

Encrypt AES with 2 different keys but the same IV [on hold]

Let's say I have 2 messages like hi and bye. I will encrypt hi with ...
2
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1answer
62 views

XTS or XEX mode?

Modern hardware and software disk encryption uses AES mode of operation. But XTS was designed to "pad" the last block when the disk sector was not divisible by block size. However all typical disk ...
2
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1answer
589 views

what kind of custom header add to encrypted file to identify my encryption,consider safe and reliable.like pseudo format extension or file size

I want to add some custom header to encrypted file to identify my encryption,consider safe and reliable.like pseudo format extension or file size.Is there any algorithm or tool to make it?
3
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1answer
80 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 ...
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1answer
3k views

Standard format to encode AES cipher and random IV

As far as I understood, a secret key (same length as CBC block size) and an initialization vector (IV) are needed to decrypt a AES-256-CBC encrypted string. As the IV should better be random, it has ...
0
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1answer
52 views

AES CCM replay attack and nonce

My wireless sensor nodes and gateway application use timestamps as nonce and will guaranty that different messages use different nonces so security is not compromised. If for some reason the gateway ...
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Extracting RC4 and 3DES keys from system memory

I have read papers [1], [2] that have presented techniques on extracting symmetric encryption keys from memory during the process of encryption. There are tools [3] that can extract AES keys from ...
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0answers
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Encrypting data on both iOS and Android without external dependencies (can I use AES-CBC?)

I am trying to achieve AWS KMS envelope encryption on both iOS and Android. From the KMS API I get a 256 bit data key in both plaintext and encrypted forms (encrypted by a master key held only on KMS ...
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1answer
63 views

How does gpg know what cipher algorithm is needed for decryption?

I am using gpg to make encrypt a tar.gz. My first try uses --verbose --symmetric and then the decryption is done with ...
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2answers
674 views

Does AES-ECB with random padding added to each block satisfy IND-CPA?

I present a modified version of AES-ECB. Suppose I want to encrypt the string hello, world. this is a test. For each block, I use the first eight bytes as my actual ...
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1answer
31 views

Signing AES Cipher

Alice and Bob have a pre-shared long-term Ed25519 key used for veryfying/signing ephemeral keys. They have a shared key which resulted from the DH exchange. They compute HKDF SHA256 of the shared key ...
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0answers
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Use a AWS KMS AES-GCM key with AES-CBC algorithm from iOS CommonCrypto [migrated]

As far as I can tell, AWS KMS Data Keys are AES-GCM keys. (source: https://d0.awsstatic.com/whitepapers/KMS-Cryptographic-Details.pdf page 13) Does that mean I must use AES-GCM to encrypt data with ...
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1answer
44 views

Disk encryption with AES

have few more questions about disk encryption with AES cipher: Do we consider all zeros (0000000) as empty block of data or is it still a data? Do we really need padding to the data blocks if a disk ...
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5answers
341 views

Ways to make white-box cryptography AES implementation more difficult to be broken

Background: I want to use white-box cryptography to hide the keys stored in a client application. I am looking for existing implementations of white-box cryptography, such as AES 128 or 256. But I ...
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0answers
23 views

AES Stream Cipher Mode Key Reuse With Random IV Per Message [duplicate]

Im using AES OFB mode, which is a stream cipher. It will be used to encrypt many seperate small amounts of data in very short amounts of time. If for every separate piece of data encrypted I use a ...