Linked Questions

6
votes
2answers
312 views

Why does Encrypt-Then-Sign not yield a CCA-secure public-key encryption scheme?

In symmetric cryptography, combining an IND-CPA secure symmetric encryption scheme with a secure MAC with the encrypt-then-MAC method yields a IND-CCA secure symmetric encryption scheme. I am trying ...
0
votes
2answers
61 views

would this be classed as a cipher text attack?

Say i'm given a cipher text to decrypt, however i also have access to a server that performed the encryption; where i could enter any plaintext and observe the result of encryption. would it be ...
1
vote
2answers
79 views

Modes of operation that simply uses the tweak of a tweakable block cipher

What is the name of the mode in which we simply change the tweak for each block without the need for complex chaining modes? Is this mode secure? Are there any other recommended modes for native ...
1
vote
1answer
85 views

ECDH, x25519 and limitations for securing client-certificates on the server

g'day Crypto.SE I'm working on a practical application of sharing a static key to better-identify a user, between the recipient (server) and the initiator (client ie. user's machine). My core ...
31
votes
2answers
7k 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, ...
0
votes
1answer
161 views

Is there any theory to measures and determine the strength of an encryption protocol?

To determine the strength of an encryption protocol, there are elements like key size, Strength of an algorithm, Performance of an algorithm or etc, I have studied these topics but I could not find ...
0
votes
2answers
228 views

What type of encryption is this homebrew “encyption algorithm”? ${}$

Background: Quite a long time ago (somewhere 1998) I thought I was really clever and invented my own encryption/decryption code. Looking through old code I rediscovered my old algorithm. (No, it was ...
7
votes
3answers
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 ...
0
votes
0answers
117 views

Formal security-definition reference

Is there a reference where all common formal security-definitions are summarized (such as OW-CPA, IND-CPA, IND-CCA1, IND-CCA2, EUF-CMA and so on)? I need a PUBLISHED reference (paper, book) which ...
6
votes
2answers
415 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 ...
7
votes
3answers
319 views

Is there a cryptographic approach to availability

Background Cryptography can be said to provide the tools used to fulfill the goals of information security. The three pillars of information security are confidentiality, integrity, and ...
1
vote
1answer
83 views

Why can´t an attacker find the key if he has the plain text, the IV and the ciphertext? [duplicate]

I am reading a book about web security and they are now talking about AES CBC. After reading the chapter I was wondering, can an attacker compute my secret key if he has access to the IV, the plain ...
4
votes
1answer
272 views

Does Elliptic Curve Integrated Encryption Scheme (ECIES) provide IND-CCA2 security?

I am looking for a faster alternative to RSA with OAEP as a IND-CCA2 public key scheme. Elliptic Curve Integrated Encryption Scheme might be a candidate, but I am not sure if it provides IND-CCA2 ...
0
votes
1answer
276 views

When do I need to use hybrid cryptography?

I need to provide confidentiality for a protocol. The protocol message size is between 100 bytes to 500 bytes. Do I need to use asymmetric encryption or hybrid cryptography?
0
votes
1answer
307 views

Proof that a modified public-key encryption scheme is not CCA secure

Let $\mathcal{E} = (G, E, D)$ be a CCA-secure public-key encryption scheme defined over $(\mathcal{M, C})$ where $\mathcal{C} := \{0, 1\}^\ell$. Let $\mathcal{E'} = (G, E', D')$ be a scheme (over $(\...

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