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

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9
votes
2answers
230 views

Terminology: differences between the terms “pre-master secret”, “master secret”, “private key”, and “shared secret”?

Both crypto.SE and security.SE have excellent Q&As about how TLS generates session keys (I have linked some at the bottom). In reading these threads I'm having troubles with terminology since the ...
9
votes
1answer
4k views

Why is Diffie-Hellman considered in the context of public key cryptography?

In all textbooks I used the Diffie-Hellman key exchange is under "public key cryptography". As far as I can see it is a method to exchange a key to be used with a symmetric cryptographic algorithm, ...
5
votes
1answer
92 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 ...
3
votes
0answers
66 views

Explanation of part of a visual cryptography algorithm

I have been working on a project involving visual cryptography and I am stuck with the following problem. My question is related to this paper, AN IMPROVED VISUAL CRYPTOGRAPHY SCHEME FOR SECRET ...
1
vote
1answer
58 views

What is k in RSA?

I am currently learning about RSA since I didn't understand the public-key-system but now I am… kind of. So I am writing the numbers as follows: $p = prime\ number\\ q = prime\ number\\ N = ...
2
votes
1answer
65 views

What does “simulator” and “interactive” mean in a cryptographic credential system's definition of security?

Definition 1 on Page 7 of “An Efficient System for Non-transferable Anonymous Credentials with Optional Anonymity Revocation” by Camenisch and Lysyanskaya, uses the term “simulator” in defining the ...
3
votes
1answer
115 views

Is secure communication without public-key crytography feasible?

We all know about public-key cryptosystems, and we know some of these are computationally secure (for the time being, of course). Are there any algorithms out there which allow safe communication ...
2
votes
1answer
122 views

Easy explanation of “IND-” security notions?

There are many schemes that can advertise themselves with certain security notions, usually IND-CPA or IND-CCA2, for example plain ElGamal has IND-CPA security but doesn't provide IND-CCA security. ...
1
vote
1answer
29 views

What is the difference between a PRF and a PRF+?

What is the difference between a PRF and a PRF+? I am understanding them to mean the same thing, but I imagine that is because I don't understand their differences. The IKE RFC defines a PRF as: ...
0
votes
2answers
183 views

Cryptosystems used to generate public key certificate

Where can we find the cryptosystems used to generate public key certificate? Are the cryptosystems under the signature algorithm and signature hash algorithm? Do I need to analyze the packets ...
4
votes
1answer
757 views

What is “Blinding” used for in cryptography?

What does "blinding" mean in cryptography, and where do we usually use it? Can you describe a sample implementation?
3
votes
1answer
593 views

Non-linearity of a boolean function

What's the definition of non-linearity of a boolean function? Roughly saying it is minimum number of times it equals any affine function. But I don't get it mathematically. For example, if $f = ...
1
vote
1answer
108 views

Generic name for (?hash) functions of form $\{0,1\}^n \rightarrow \{0,1\}^{poly(n)}$

Consider a function $$f: \{0,1\}^n \rightarrow \{0,1\}^{poly(n)} $$ with the following properties: hard to invert, i.e. given $f(x)$, hard to find $x$ hard to find a collision, i.e given $f(x)$, ...
14
votes
2answers
6k 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 ...
2
votes
4answers
75 views

Definition of the term “key”

I've looked in many places (NIST, text books, online resources) and I cannot find an answer to the definition of the term "key" from a semantic point of view. Is it the "key" to cipher-texts (i.e. ...
2
votes
2answers
72 views

How to calculate if probability is negligible or not

If i have probability $Q = 2C(A\times B)$ where $A$ and $B$ are unknown probabilities and $C$ is a non-negligible probability, what can i speculate about probability $Q$ and how can i calculate bounds ...
2
votes
2answers
102 views

Inconsistent terminology for ciphers and algorithms

I've been baffled by all the different kinds of names which are given to cryptographic algorithms. There are block ciphers and stream ciphers (AES and RC4). There is symmetric and asymmetric ...
0
votes
1answer
80 views

Is adaptive security the same as full security?

This question contains a great answer about adaptive security, but I haven't yet found a proper definition what full security is. Does a stronger security than adaptive security exist or are the two ...
4
votes
1answer
2k views

What is “Implicit Authentication”?

What is “Implicit Authentication” in the context of authentication methods? I searched the Web but could not find any article that describes this. If anyone can describe it, that would be a great ...
10
votes
7answers
2k views

How exactly is “true randomness” defined in the realms of cryptography?

Especially in relation to stream ciphers, I frequently read about (sometimes theoretical, sometimes practical) attacks that are able to "distinguish a ciphertext from a truly random stream". What's ...
8
votes
3answers
2k views

The exact difference between a permutation and a substitution

I've noticed confusing definitions about permutation and substitution, preventing to make the difference. A permutation changes the order of distincts elements of a set, but this can be writen as a ...
2
votes
1answer
474 views

What is a fair exchange scheme?

The Wikipedia entry Fair exchange has only two lines, and the only paper I can find describing such a protocol is extremely complicated. Is this a new field in cryptology or can someone give an ...
1
vote
1answer
90 views

Counter Mode (CTR) and mult-CPA

I am not sure if Counter Mode (CTR) encryption is mult-CPA (chosen-plaintext attack) secure or not.
6
votes
5answers
3k views

What is the difference between CSPRNG and PRNG?

What is the difference between CSPRNG and PRNG? Is there performance differential between them? For example: We use PRNG for key generation which is very expensive and CSPRNG for IV/nonce in block ...
0
votes
4answers
205 views

what is it called when encrypt('a') + encrypt('a') == encrypt('aa')?

So normally if you do encrypt('a') twice in a row you'll get the same result. But sometimes (as is the case in SSH) this is not desirable. You want encrypt('a') + encrypt('a') == encrypt('aa'). What ...
9
votes
2answers
311 views

Definition of “pepper” in hash functions

I am confused about the notion of "pepper" in the context of storing hashes of users' passwords. Definition 1: A pepper is a secret key Looking around the Internet, for example here or here, a ...
2
votes
2answers
604 views

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?
0
votes
1answer
72 views

What is “electronic” in electronic codebook (ECB)?

This is an honest question regarding terminology. I believe that I understand why one mode to use a block cipher is called a codebook. But I wonder why electronic as a work appears here? Is it fair ...
5
votes
2answers
623 views

What does “circuits” mean in Cryptography?

I am not a hardcore cryptographer so this might be a really stupid question. I am looking through some papers in homomorphic encryption and discovered they describe computation as "circuits", why do ...
1
vote
1answer
68 views

The use of the term “sound” in cryptography [closed]

We often see the term "sound" in cryptography. What is the sense of this word ? Thank you.
1
vote
2answers
110 views

Are password salts equivalent to keystream?

I was reading up on keystream when I came upon the definition of it: A keystream is a stream of random or pseudorandom characters that are combined with a plaintext message to produce an encrypted ...
1
vote
0answers
91 views

What does “nonlinear mapping” mean?

Page 15 of the Keccak reference (PDF) explains that the $Chi$ step mapping of the Keccak-f permutation in Keccak is defined to be “nonlinear mapping”. Without this, the complete permutation would be ...
1
vote
1answer
171 views

Correctness vs Completeness

What is the conceptual difference between the definition of correctness and completeness in verifiable cryptographic protocols? They justify that if a statement is correct then the verification should ...
0
votes
1answer
92 views

Is there any definition for “generic attack” in context of cryptography or more specific “hash functions”?

I'm searching a definition of "generic attack" in context of cryptography or more specific in context of "hash functions". I searched some books and the web but I did not found any definition for it ...
3
votes
1answer
128 views

What is the technical name for a public key container in DER format?

I have a public key in the following (format-neutral; the type is specified by the DER bytes) format: ...
6
votes
6answers
1k views

Cryptography vs Security

This may sound a little bit of basic but here it goes… Which of the following is correct? “Cryptography is under the security field”, or “Security is under the cryptography field?” Cryptography ...
1
vote
0answers
83 views

Types of cryptography

We have cryptography based on hard problems from number theory, like DDH. When we speak about symmetric cryptography with AES, a mode of encryption (CBC, ...), what is the type of problem ? What is ...
1
vote
0answers
94 views

Modulo settings for successful encryption?

I saw this awesome video which shows how encryption works using "discrete logarithm". The example says: $3^x\mod17$. I understood that $3$ is called “generator”, because it has no "straight" root and ...
7
votes
1answer
182 views

What is the “artificial abort” technique?

In the security proof of Brent Waters's paper Efficient Identity-Based Encryption Without Random Oracles, he uses a novel “artificial abort” step on page 6. At this point the simulator is still ...
5
votes
2answers
280 views

Does data authenticity always, implicitly, provide data integrity?

Does a scheme which provides data authenticity (e.g. HMAC or RSA signature) always implicitly provide integrity? It seems, to me at least, that it must by necessity. However, I have seen ...
2
votes
1answer
66 views

What are the two parts of SHA1's compression function called?

SHA1's compression function has two distinct parts: one where 16 words are expanded into 80 words, and one where the 80 words are used over 80 rounds. Are there specific names or terms for each of ...
3
votes
3answers
155 views

The meaning of “scheme”

This question is a bit different from other questions here, but I think it is suitable to correctly understand the terminology of cryptography. Consider the following two sets of terms: Encryption ...
3
votes
1answer
212 views

Difference between lightweight, online and low memory Authenticated Encryption schemes

What is the basic difference between the following types of Authenticated Encryption (AE) schemes? Lightweight Authenticated encryption Online Authenticated Encryption Authenticated Encryption for ...
1
vote
1answer
97 views

Terminology: What is the word describing a hash key, a crypto key, and a certificate?

If I want to check the integrity of some piece of data, I can check that a cryptographic hash of the data corresponds to a known hash. Alternatively I can also check a digital signature on the data ...
1
vote
2answers
244 views

Tweakable encryption algorithms vs Key wrapping

I have read many articles about Key wrapping and tweakable cipher modes. However, I don't understand the main difference between them? What you recommend for Key storage and Key Archive.
1
vote
1answer
163 views

What are unified addition and differential addition in elliptic curve point arithmetic?

A lot of papers use these terms but I do not find a proper explanation of them. Can somebody tell the meaning / difference / intuition / application and if possible with an example.
5
votes
1answer
1k views

What is it meant by a “hybrid argument”?

Can anyone explain (or point to a reference for) what a hybrid argument is in a security proof, and when it's convenient or preferable to use it? Among some of the places where I've seen it ...
2
votes
2answers
157 views

Is there a metric (term) for work required to decrypt a public key?

Any public key decryption can be decrypted given enough time and computing power. Is there a metric or term for this? Something like it would require on average 2^43 1024 bit hashes to find private ...
-1
votes
3answers
229 views

How to judge if my work is meaningful in cryptography? [closed]

Suppose I have generated a new cryptographical result - for example a new cryptographical primitive, or a cryptanalytic attack. How can I find out whether this result is meaningful (significant)? If ...
1
vote
1answer
577 views

In this example, which is a premaster secret, and which is a master secret?

In the context of this data, as shown in the image below, which one is a pre-master-secret and which one is a master-secret. It looks to me as if the final value of 2, for Alice and Bob is a ...