Linked Questions

2 votes
2 answers

Is E_k(M)||H(m) form of MAC secure?

Would this encryption and signing scenario be considered tamper-proof? ...
Evan Su's user avatar
  • 421
2 votes
2 answers

With AES-CTR does the block input need to be implemented as nonce || counter?

I am looking at an AES-CTR implementation (WebCrypto) and it takes an initialization parameter count which is an array of 16 bytes. It then asks you to specify <...
Chris_F's user avatar
  • 179
5 votes
1 answer

The Rationale behind NIST's counter/LFSR recommendation on deterministic IV constructions on SP 800-38D

The NIST has a "SP 800-38D: Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC". This guideline is a base for AES-GCM from definition to security ...
kelalaka's user avatar
  • 47.6k
0 votes
2 answers

How is AES256-GCM auth tag used in decryption

I have been playing with AES256-GCM in NodeJS crypto library and it shows that the original message can be decrypted without caring about the auth tag. So can a non-tag verified decryption be secure? ...
Kim Mỹ's user avatar
  • 155
2 votes
1 answer

AES CTR - Counter Management

Let ssuppose that we are using AES in CTR mode to encrypt a number of blocks ($x$ bytes each). How is the current used IV (nonce+ctr) synchronized among both communicating entities? I suppose that the ...
Marc's user avatar
  • 297
2 votes
1 answer

What does AES-GCM provide?

I am wondering does AES-GCM which uses Authenticated Encryption provide us with all 3 properties (Authenticity, Confidentiality, and Integrity), or does it not provide integrity?
CryptoGuru's user avatar
0 votes
1 answer

Alternative to CBC mode encryption?

Given that CBC mode encryption is vulnerable to padding oracle attacks, what is the next best alternative ? a) Include a hash check in the API scheme, validate the hash and then proceed with CBC. If ...
Ravindra HV's user avatar
2 votes
2 answers

How much data can we encrypt using AES 256 before changing the key?

Although this question has been answered in this link (After How Much Data Encryption (AES-256) we should change key?), I am not satisfied with the answers because the Recommendation for Block Cipher ...
user48217's user avatar
0 votes
1 answer

Consequences of AES-GCM always encrypting the same plaintext

I am analysing an authentication protocol. In this protocol AES-GCM is used to encrypt part of the messages. Regarding the authentication protocol, I made the following observations: The plaintext ...
Kobodjo's user avatar
  • 31
1 vote
2 answers

Is it cryptographically insecure to use fixed-length AES-GCM messages?

Is there any weaknesses to encrypting fixed-length messages? Should a random amount of padding be added to the message to decrease the odds of some sort of attack?
user avatar
0 votes
1 answer

Is a random string good for an AES-256 instance

I have a randomly generated string of about 256 characters long. This string is hashed to for a key and initialization vector for a program running on the .NET framework 4.8. Is this method secure ...
DDX5 Media's user avatar
1 vote
1 answer

Do I need to change IV in AES-256 GCM when I only use encryption for challenge-response exchange with random string?

When I want to use encryption only for challenge-response exchange and not for hiding the contents of an encrypted message, is it still a threat to me not changing IV for new encryption? For easier ...
krystof18's user avatar
  • 143
1 vote
1 answer

Why are iterated substitution-permutation product ciphers only used on fixed-size plaintext blocks?

Another way to ask this question: when block ciphers were invented, why did they add the restriction that the block cipher would be restricted to blocks of a fixed size? From my laymen's point of view,...
Wladston Ferreira Filho's user avatar
2 votes
1 answer

End-to-end photo storage

I've been tasked with developing an app that will need to store photos a user takes securely, and I've been struggling to think up a method to do this. What I was thinking so far is as follows: When ...
George Herbert's user avatar
0 votes
0 answers

Is it possible to uncover the plaintext if IV is used twice but the key is different?

I am currently working on a cryptography challenge. The program uses AES-GCM to encrypt and decrypt strings. Let's say I have the following: IV which is reused only 1 cipher text authentication tag ...
fdfdfd's user avatar
  • 101

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