Linked Questions

4 votes
1 answer
9k views

What is the meaning of IND-CCA secure under standard model? [duplicate]

I notice that in many research papers (viz. "Universal hash proofs and a paradigm for adaptive chosen ciphertext secure public-key encryption" by Cramer and Shoup) the authors showed that their ...
Pinkimani Goswami's user avatar
1 vote
0 answers
2k views

Understanding CPA and CCA Secure [duplicate]

CPA attack means the attacker can send in his own plaintext to the oracle and receives some sort of ciphertext back. CCA attack means the attacker can send in his own ciphertext to the oracle and ...
user3277633's user avatar
1 vote
0 answers
549 views

What do you mean by Ciphertext indistinguishability [duplicate]

Wiki definition : A cryptosystem is considered secure in terms of indistinguishability if no adversary, given an encryption of a message randomly chosen from a two-element message space ...
python's user avatar
  • 151
33 votes
2 answers
12k views

7zip : Why does encrypting the same file with AES-256 not give the same output?

Using 7-zip 19.00, on Windows 10 1909, build 18363.592, I encrypted a text file with the contents "hello there" using AES-256 and the password "123". I did this two times, the exact same procedure, ...
super's user avatar
  • 463
33 votes
1 answer
10k views

What do the signature security abbreviations like EUF-CMA mean?

From time to time, one stumbles across formal security definitions. This includes security definitions for signature schemes. The most common ones are the *UF-* ...
SEJPM's user avatar
  • 46.1k
11 votes
5 answers
2k views

What is the purely mathematical definition of encryption strength?

An encryption function can be used to obfuscate pieces of information and later on retrieve them. What is the yardstick for measuring how well the function encrypts the information ? Given any ...
ARi's user avatar
  • 235
18 votes
1 answer
31k views

Bit Flipping Attack on CBC Mode

To perform a bit flipping attack, the previous block is modified by using XOR. This results in an altered plaintext. However, now the ciphertext of the previous block is altered, hence it will result ...
CXB's user avatar
  • 321
8 votes
1 answer
2k views

How to prove security of a randomized encryption algorithm?

I have designed an random encryption in public key setting. I am convinced about its security guarantee but I need a formal way to prove its robustness. How can I prove the security of this random-...
Abdullah Gani's user avatar
11 votes
2 answers
1k views

What do NM-CPA and NM-CCA mean?

When I've been researching authenticated encryption, the following terms keep showing up: NM-CPA NM-CCA ....without any definition as to what they mean. I've tried searching the web for their ...
starbeamrainbowlabs's user avatar
7 votes
3 answers
2k views

Does adding complexity mean a more secure cipher?

I have a cryptography workshop question I'm having trouble with as follows; Person A creates a cipher $E_k(m)$ which produces a ciphertext from message $m$ using key $k$. The function inside $E$ is ...
melloncollie's user avatar
3 votes
3 answers
5k views

How can a system be non-deterministic?

Newbie here, so forgive me if this is a stupid question. In math class we learned about RSA encryption (as a practical application of what we learned about the Euler phi function and Fermats little ...
Justin Sanders's user avatar
1 vote
5 answers
12k views

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 ...
Flurrywinde's user avatar
3 votes
1 answer
6k views

ElGamal CPA secure

I understand that if DDH (Decisional Diffie–Hellman) is hard then ElGamal is CPA secure. But I'm having confusion on what part the DDH applies to. So, given $pk=(G, g, y), y=g^x$ and $sk=(pk,x), x \...
user153882's user avatar
7 votes
1 answer
3k views

Is ElGamal IND-CCA1?

We all know that textbook ElGamal falls due to chosen ciphertext attacks, because of its multiplicative homomorphic property ($E(A)*E(B)=E(AB)$). However these attacks require the ciphertext ($E(A)$ ...
SEJPM's user avatar
  • 46.1k
3 votes
2 answers
2k views

Does having a hash of the plaintext compromise the ciphertext?

If I have a SHA512 hash of my plaintext, does it weaken or break the encryption of my ciphertext?
Homer6's user avatar
  • 133

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