Questions tagged [terminology]

Questions about the meaning and proper use of specific technical terms or notation within cryptography.

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What is the fundamental difference between multipartite and multilevel secret sharing?

According to this paper , Multipartite secret sharing scheme is a scheme in which the set of participants is divided into disjoint parts and all participants in the same part play an equivalent role ...
-1 votes
2 answers
315 views

Hybrid Symmetric and Asymmetric Encryption

Just looking for a bit of an explanation on the concept of hybrid symmetric and asymmetric encryption. My understanding: Client requests public key from https://site1.com The client receives the ...
5 votes
1 answer
651 views

What does "adaptively secure" mean?

In a paper it says "In the generic group model, the PRF is adaptively secure for inputs of $\mathbb{Z}_q^n$". Maybe a stupid question, but what does "adaptively secure" mean exactly?
4 votes
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Hash Function Properties

What I am trying to understand is shown in all three properties of a secure hash function, I will focus on Preimage attack resistance. Preimage resistance: given a hash h, it's difficult to find m s.t....
1 vote
1 answer
236 views

One way function existence

Let $x = (x_1, x_2,...,x_n)\in\{0,1\}^n$ for $n\in\mathbb{N}$. Prove that if one-way functions (OWFs) exist, then there exists a one-way function $f$ such that for every bit $i\in[1,n]$ there exists ...
0 votes
2 answers
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What exactly is asymmetric about 'asymmetric cryptography'?

What exactly is asymmetric about 'asymmetric cryptography'? https://www.sysadmins.lv/blog-en/digital-signatures.aspx says: "In other words, anything that is encrypted by a public key can be ...
1 vote
1 answer
337 views

What is a clearsigned message?

PGP Digital Timestamping Service webpage mentions The service operates in a number of different "modes" depending upon the required results. The current modes are:- ...
3 votes
1 answer
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Idiomatic description for an adversary in possesion of a quantum computer?

I was wondering what the "accepted" way is to describe an adversary who: is in possession of a quantum computer with which they can efficiently run quantum algorithms such as Grover's or Shor's ...
4 votes
1 answer
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What is Post-Compromise security exactly?

After reading these papers on Post-Compromise Security: Post Compromise Security Asynchronous Ratcheting Trees My understanding is the following: it is possible for a key-agreement protocol to ...
9 votes
2 answers
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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 ...
3 votes
3 answers
314 views

Is obfuscation considered a cryptographic primitive?

The general definition of obfuscation is the process of obscuring a message (not necessarily source code). There is a "rigorous" method for obfuscation (indistinguishability obfuscation, ...
3 votes
3 answers
377 views

Measuring entropy of a uniform distribution source

What is entropy? I do not understand it at all. One article states: When there is an equal chance for all items to appear, we have a uniform distribution. In uniform distribution the entropy is high....
0 votes
1 answer
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What does this Big-O notation mean based on appendix?

I am reading the following book: Introduction to Modern Cryptography Second Edition by Jonathan Katz and Yehuda Lindell. I am going through page 533 where they list what some of the notation means, ...
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1 answer
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Definition of a distinguisher

In Introduction to Modern Cryptography by Katz and Lindell, p. 70, they define a pseudorandom generator by: Let $l(\cdot)$ be a polynomial and let $G$ be a deterministic poly-time alg. s.t. for ...
77 votes
8 answers
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Layman's explanation of encryption backdoors

In the media, I sometimes read about "backdoors" in encryption algorithms. I'd like to understand what such a backdoor actually consists of. Is it: a) a hidden weakness in the math formulas ...
1 vote
1 answer
482 views

What is definition of "adversary"? And what do they do?

Currently I am writing my last assignment about secret sharing. But I don't clearly understand adversary. I know this is a fundamental concept in secret sharing. But I couldn't find references that ...
26 votes
5 answers
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What is Indistinguishability Obfuscation?

I've been studying functional encryption. I recently read that a multi-input functional encryption (MIFE) implies indistinguishability obfuscation (IO). Can someone please brief me: what is ...
1 vote
2 answers
363 views

Non-repudiation isn't a part of cryptography?

According to the "Handbook of Applied Cryptography" by Alfred J. Menezes, Paul C. van Oorschot, and Scott A. Vanstone (CRC Press, 1997; p.4): Cryptography is the study of mathematical ...
11 votes
1 answer
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What is Deterministic Authenticated Encryption?

I came across something known as deterministic authenticated encryption in my studies, and a lot of people were associating it with Synthetic IV mode. I am having trouble understanding what exactly ...
10 votes
1 answer
11k views

What is a trapdoor permutation?

Can anyone explain to me what a trapdoor one-way permutation is? Is RSA a trapdoor one-way permutation? Context: I was reading about ring signatures. On page 560, it describes steps to implementing ...
1 vote
0 answers
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Question about hiding commitment scheme for integers

Given a generic group $\mathbb{G}$ of an unknown order (such as a $3000$-bit RSA group) and a randomly generated element $g \in \mathbb{G}$, is the commitment scheme $\mathrm{Com}(x)= g^x$ not ...
10 votes
4 answers
3k views

Does a hash function necessarily need to allow arbitrary length input?

I always assumed that a hash function allows input of arbitrary length, since that's what all the hash functions I was aware of did. Wikipedia's definition of a hash function is as follows: A hash ...
1 vote
1 answer
244 views

What is the more accurate way of stating the correctness of a PK encryption scheme?

Is it more accurate to state that a public key encryption scheme is correct if for all $m \in M$ and $(pk, sk) \in \operatorname{Gen}(1^k)$ a. $\operatorname{Dec}_{sk}(\operatorname{Enc}_{pk}(m))=m\;$ ...
2 votes
2 answers
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Is there a term for cryptographic attacks where you can verify decryption without assuming any known structure on the plaintext?

The questions https://security.stackexchange.com/questions/1696/if-someone-breaks-encryption-how-do-they-know-theyre-successful and https://security.stackexchange.com/questions/119887/how-to-know-if-a-...
14 votes
1 answer
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What is cryptographic agility?

I keep seeing the term "Cryptographic Agility" referenced. What does it mean? For instance: https://msdn.microsoft.com/en-us/library/windows/desktop/bb204775(v=vs.85).aspx One of the key value ...
1 vote
1 answer
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Term for non-ARX symmetric-key cryptographic primitive design strategy

What's the term for describing designing symmetric-key cryptography primitive out of bitwise operations and shifts and rotations? The closest thing I've found is this Keccek team's page calling it ...
0 votes
2 answers
3k views

There is Alice and there is Bob. But what is the name of the malicious user?

I know it is a kinda funny and maybe even naive question but its still security related, so I decided to ask. Bob and Alice are widely used names indicating the two end-users/parties for web protocols....
8 votes
3 answers
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Definition of authenticity

I came across various definitions of what authenticity means in cryptography. I would like to know which one is correct. The first definition - the one I always used - is the following: Data ...
7 votes
1 answer
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What does it mean to be "sound"?

I've been reading this in many places and I still don't properly understand what it means to be "sound". As an example of what I am asking for: The Fiat-Shamir transfrom is sound in the ...
7 votes
2 answers
740 views

Scrypt not "old enough" to be safe?

I just check all the questions with scrypt tag about that and usually it's said that scrypt is nice in theory and theoretically better than bcrypt and PKDF2, but it's too young to be "completely safe"....
14 votes
1 answer
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What is the difference between key size and block size (for AES)?

We are working on AES and want to develop a website which should provide an encryption facility but we are not understanding the difference between key and the block size. More appropriately what does ...
19 votes
2 answers
5k views

What is "witness encryption"?

I recently skimmed over tho papers on time-lock encryption: “Time-release Protocol from Bitcoin and Witness Encryption for SAT” by Liu, Garcia, and Ryan “How to Build Time-Lock Encryption” by Jager ...
172 votes
2 answers
183k views

What is the main difference between a key, an IV and a nonce?

What are the main differences between a nonce, a key and an IV? Without any doubt the key should be kept secret. But what about the nonce and the IV? What's the main difference between them and their ...
1 vote
2 answers
412 views

Is it fair to say that MACs use a signing algorithm?

The Wikipedia page on MAC calls the algorithm that is used to generate the MAC as a signing algorithm. Is that a fair use of that term? Can we then say that HMAC-SHA-1 uses SHA-1 as the signing ...
4 votes
2 answers
276 views

What is the difference between security parameter and $b$-bit security?

In a previous question, I read ... for $b$-bit security meaning $O(2^b)$ work for an attacker to break the system... While in Katz's Introduction to modern Cryptography, I read: The key-generation ...
3 votes
2 answers
196 views

Short term for "Purposely-slowed hash"

When Argon2, Balloon, scrypt, bcrypt¹, PBKDF2… are used for a password, we can call them password hash (for password storage) or password-based key derivation function (for use in encryption). But ...
2 votes
2 answers
2k views

Difference between computationally and perfectly hiding (binding) properties

I am new to Cryptography and has a trouble of understanding the difference between perfect and computationally hiding (binding) properties of a commitment scheme. I also would like to ask what does it ...
7 votes
2 answers
2k views

zk-SNARKs vs. Zk-STARKs vs. Bulletproofs: definitions

I have become quite familiar with Bulletproofs the last few months. Bulletproofs is the name given to a zero-knowledge proof system for arithmetic circuits, by Benedikt Bünz et al. It is a specific ...
0 votes
2 answers
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What is the difference between an encryption protocol and an encryption standard?

What is the difference between an encryption protocol and an encryption standard? Am I missing something here? Or are they in fact two different concepts altogether?
5 votes
2 answers
2k views

What is the difference between data compression and compression in cryptographic algorithms?

What is the differences between data compression as used in e.g. the ZIP protocol and compression as performed in cryptographic hashes? Are there common properties as well, apart from creating a ...
0 votes
0 answers
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What does it mean exactly that an adversary can control a polynomial number of parties?

I have an intuitive idea of this, but I am not sure if I am formally interpreting it correctly. In the scenario I am considering, each party is identified by a sequence of $n$ bits and I have $2^{n}$ ...
11 votes
2 answers
4k views

Meaning of the term "Key Material"

I am reading specifications from my client that focuses on the topic of security. In these specs, the term key material has appeared many times. I used Google to look for what the term means. ...
0 votes
1 answer
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What is the definition of dummy password?

Recently, I try to read some papers about Password Authenticated Key Exchange (PAKE). I can’t understand the meaning of “dummy password .” Can someone gives a concrete definition of it. And what is ...
0 votes
2 answers
515 views

is it necessary to write C=E(K,P), Can we write C=E(P,K)?

I just want to know that can we write encryption and decryption formula like $C=E(P,K)$ instead of $C=E(K,P)$
51 votes
1 answer
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What are SNARKs?

What does it mean and what is it used for, I have been hearing this term a lot lately. From the context I've heard it talked about it seems to be connected with zero knowledge?
3 votes
1 answer
2k views

What does "crypto_box" actually mean in libsodium and NaCl?

I cannot find what "crypto_box" actually means. In general, and in specific cases, what does "box" do? I know that libsodium is authenticated encryption, but GPG is not. "Box" makes me think the ...
2 votes
1 answer
151 views

Meaning of difference Δ delta

I tried to understand some crypto text but I am new to this. Does this: Let $X,X'$ be $\ell$-bit values, and $\Delta X=X\oplus X'$ means that $X$ and $X'$ have $\ell$ bits and $\Delta X=X-X'$ or ...
4 votes
1 answer
542 views

Is there a difference between $\mathbb{Z}_2^b$, $\text{GF}(2^b)$ and $\text{GF}(2)^b$?

I have read a lot about Galois Fields (GF). They are also presented in The The Design of Rijndael: AES - The Advanced Encryption Standard on pages 13 and 14. In computer memory, the polynomials in $...
1 vote
1 answer
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Terminology for parties in authentication protocols

Is there a common terminology to designate parties in authentication protocols? For example, we typically use prover and verifier to designate parties with zero-knowledge proofs.
1 vote
1 answer
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Confused about terminology in the many flavors of security [closed]

I am learning about cryptography from diverse sources, and I have found terminology a bit confusing. In principle, I understand the difference between the symbolic model and the computational model. ...

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