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Questions tagged [algorithm-design]

Design of cryptographic primitives (algorithms), like block ciphers, stream ciphers, random-number generators, hash functions, MACs, key exchanges, public-key encryption or signature schemes. Also tag with the relevant type of primitive. If you ask about a known existing algorithm, also tag with its name.

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What can you do with an Antminer D3 that's never been used? [on hold]

So I paid $ 3000 USD for an Antminer D3 at the end of 2017. When I received it I learned that the S9 was already out and that my new mining beast has pretty much been rendered obsolete. On top of ...
2
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1answer
62 views

Generating a key pair using a signature generated by an existing key

I’ve built an app in which each user has a private/public key pair and I want to generate a second one for them, however I cannot store the second private key anywhere. What would be the drawbacks ...
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0answers
51 views

Explaining Berlekamp-Massey Algorithm in simple/layman term?

My foundation in Mathematics is not great. But I would like to understand how Berlekamp-Massey Algorithm works and how it is used in lay-man terms. The only thing I find out there is the emphasis on ...
2
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0answers
43 views

Understanding LFSRs and Berlekamp-Massey Algorithm [duplicate]

I have a tutorial question which focuses on LFSRs and Berlekamp-Massey Algo (which is totally out of my syllabus). Please forgive me if my questions seem stupid. I'm given these information: {"...
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0answers
41 views

what is the name of the following protocol? [closed]

I have 2 parties (A and B) who don't trust each other. My goal is to design a protocol so I ensure they trust each other. I'm thinking of a name to such protocol like "with No A2B Prior Trust"?
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0answers
26 views

Proxy decrypt algorithm in Extended Proxy-Assisted Attribute Based Encryption (ABE) Scheme

Context I'm trying to implement the Attribute-Based Encryption (ABE) scheme described in the paper - Extended Proxy-Assisted Approach: Achieving Revocable Fine-Grained Encryption of Cloud Data (Yang ...
0
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1answer
61 views

How do I figure out the number of unique combinations

I am developing an algorithm that uses a lookup table to process the data, I want to know how many unique tables can be created. If I have a table of 256 values I know that 256! would tell me how many ...
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0answers
50 views

how $C =M^e \bmod N$ can be written as $C = M \cdot k \bmod N$ in RSA algorithm?

how $C =M^e \bmod N$ can be written as $C = M \cdot k \bmod N$ in RSA algorithm? how $M =c^d \bmod N$ can be written as $M = c.k^{-1} \bmod N$ in RSA algorithm?
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2answers
40 views

Is there any way to check signed documents in a group of people without knowing who signed which?

Let's say there are 3 people A, B, C. Everybody knows their public keys. They sign documents/messages and normally we can know who signed which by checking with their public keys. Is there any way to ...
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0answers
10 views

Are compressed pairings used for Barreto-Naehrig curves in practice?

In 2009 Galbraith and Lin wrote the article "Computing Pairings Using x-Coordinates Only" https://link.springer.com/article/10.1007/s10623-008-9233-3, where they proposed to compute pairings on ...
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4answers
3k views

If Kerckhoff's Principle holds, why do we need a cipher at all?

I understand Kerckhoff's principle, in a very practical sense, that the best attack that can be performed on a given cryptographic algorithm should be only as practical, if not less practical, than an ...
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1answer
54 views

How to prove that work is done without actually knowing the payload

Is there a way for an algorithm to run securely on one end, whilst the other end is able to be notified and also verify that it has run and done the work without knowing what the actual payload is? ...
3
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1answer
121 views

Improving efficiency of an “encryption” algorithm based on a chaotic map

I've implemented an "encryption" algorithm that uses the deterministic chaos of an extended logistic map: $x_{n+1}= r_n \cdot x_n \cdot (1-x_n)$ $y_{n+1} = \begin{cases} \text{$x_n+y_n$}...
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1answer
69 views

Can Base64 be seen as a way of encryption if we use different index table?

As we know, the index table (which maps bytes in [0, 63] to characters) of Base64 encoding is public, so everyone can decode Base64 strings from others. But what if we use a shuffled index table and ...
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1answer
93 views

How could I test my own Cipher? [closed]

I recently developed a new cryptographic algorithm. I just initiated with just nothing in mind. But being near to completion (though my algorithm is constantly developing. Now it is version 11.02), I ...
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4answers
280 views

Size of A Hashed String Using SHA-512

When hashing a messages of size of n, does the SHA2 algorithm always produce the same sized hashed value? The reason I am asking is that I am building an OAuth 2.0 ...
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1answer
67 views

Question about brute force running time

Quite a simple question though I can't wrap my head around it: The key size is: $n$ Because it's brute force it tries each possible key once from $0$ to $n$, but in my head that just makes the run ...
2
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0answers
41 views

Reduction from integer factoring to computational Diffie Hellman

The computational Diffie Hellman (CDH) problem for ${\mathbb{Z}}^*_p$ is given a prime $p$, a generator $g$ of ${\mathbb{Z}}^*_p$, and a pair $(g^i, g^j)$ to compute $g^{ij}$. The value $g$ is called ...
2
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2answers
185 views

Does there exist a CSPRNG that does not require generating prime numbers, but also does not depend on any other cryptographic primitives?

The following excerpt is taken from the “Cryptographically secure pseudorandom number generator” article on Wikipedia: CSPRNG designs are divided into three classes: those based on ...
2
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2answers
106 views

Cryptography scheme to prove you really are the author for something

Say I'm a researcher like Satoshi Nakamoto that wants to stay anonymous. I want to publish documents and sign them somehow. A few years, I want to reveal my identity and prove it was me who was ...
3
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1answer
60 views

Could we use a more efficient hash for signature generation?

Is it possible to use a more efficient hash - such as one based on GHASH - instead of a cryptographic hash for signature generation? In other words, could a combination of a fast hash and the private ...
2
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2answers
75 views

Is there a way to sign a message without being allowed to see it?

I want to sign a message while not being able to see the message. Logically, there should be a way, I just don't know how this translates into cryptography. Here is an illustration for what I mean: ...
3
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3answers
252 views

Is it possible to exactly reverse engineer an unknown cipher inside a black box?

Consider the following arrangement:- There is an unknown cipher algorithm operating inside the black box. You can enter infinite key /plain text pairs, and observe all of the outputs. The box might ...
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1answer
33 views

Secure offline treasure hunt

Say I would like to create an app that would allow users to organize treasure hunts for their parties. The host of the party would create a list of GPS coordinates for each hiding spot and distribute ...
0
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1answer
225 views

How many rounds of encryption is ideal?

I am a newbie to the cryptography world. I am working on a custom algorithm that encrypts the data multiple times and results in a cipher text. It uses a different key in each round to encrypt it. I ...
3
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1answer
82 views

Can length extension attacks be avoided by a single bit flip?

It always seemed to me that length extensions are possible simply because no special operation is performed after the last operation - for instance in a Merkle-Damgård construction. Basically the MD ...
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2answers
76 views

Encrypting current time using 3DES as a signature

I came across a peculiar system for generating "signatures" ("signatures" is within quotes because this is a bad use of 3DES) in the wild. It works as follows: a symmetric key is generated and used ...
2
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0answers
36 views

Can we encrypt data that must be decrypted with any private key plus a server generate bits?

I have come up with a scenario to make a secure data. Suppose I have a public encrypted file that anybody can download. But whenever anyone want to decrypt that data they need to get a key from server ...
3
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2answers
192 views

Is this algorithm good enough for small radio messages?

This question is related to: How to implement security - authenticity/confidentiality/integrity for 6/14 bits radio messages? I am looking for a message that an attacker listening to the radio ...
5
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3answers
247 views

Where can I find the description of SHA0 algorithm?

Where may I find the description and or pseudocode for the SHA0 algorithm. I am looking for something on these lines - HMAC RIPEMD. I have been implementing a few of those (HMAC, HOTP, TOTP and MD4, ...
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0answers
124 views

How few cryptographic primitives can we use to derive all other constructions?

We have a lot of cryptographic primitives now, and many methods of deriving one type of scheme from another. There are even some like the Merkle signature scheme, which uses a hash function to derive ...
3
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2answers
526 views

understanding the block bits for DES

I'm trying to understand cryptographic protocols, and I've started with the DES algorithm. DES specs: it uses 64 bits for the plaintext, 56 bits for the key, with a result of the same 64 bits of ...
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2answers
87 views

rotor machines: secrecy of wiring

During the heydays of rotor machines, the internal rotor wiring was always a closely guarded secret. Even fully cleared repair staff was not allowed to do anything that could reveal it. As the ...
1
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2answers
90 views

Public-private algorithm where it is not possible to recover public key from private key?

Is there an asymmetric algorithm where it is not possible to extract a public key from private key? So far any algorithms I tried (dsa, rsa, ecdsa, ed25519) successfully recover their public keys from ...
2
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1answer
31 views

Optimized Garbled Circuit Algorithmic Description

Till 2018, Garbled Circuit (GC) is of its age 30's and many optimization methodologies have been proposed, including point-and-permute, row-reduction, free-xor, fixedkey-blockcipher, half-and. But, ...
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1answer
52 views

Cryptographic algorithm for knowing who has more money?

I recall reading about this but forgot what it’s called. Suppose two people want to know who is richer but don’t want to reveal their net worth to the other. How can they securely exchange info to ...
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1answer
55 views

Reference for the Tortoise and Hare algorithm by Floyd?

Can someone please point me to a book or paper that describes the Tortoise and Hare algorithm by Floyd? I know there are ample websites out there, but for reference purposes, I need a book or paper ...
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0answers
175 views

Fastest known Elliptic Curve Cryptography “solution” (coordinate systems (multiple?), algorithms, precomputed values etc)?

I am writing an Elliptic Curve Cryptography SDK in pure Swift, and currently I am only using Affine Point and simple Double-and-add. I am soon about to work on a faster solution. I am asking for help ...
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2answers
400 views

Which attacks are prevented by the different initial hash values for SHA-2 with truncated output?

NIST specified SHA-2 hash functions with truncated output. Those hashes use different initialization values than SHA-256 or SHA-512. SHA-224 is based on SHA-256. SHA-384, SHA-512/224 and SHA-512/256 ...
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1answer
69 views

Are MD5 possibilities really $2^{128}$? [duplicate]

I have a simple question: Are we certain that the md5 hashing algorithm can produce $2^{128}$ different outputs ? If so, how ? Note: Sorry if this has already been asked, I really couldn't find it.
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0answers
66 views

Is this modification of the sponge function cryptographically weaker than the standard sponge function?

Let $\lfloor A \rfloor_B$ denote the first $B$ bits of a bitstring $A$. Let $F$ denote the underlying function of the sponge construction (for SHA-3, $F = \text{Keccak-}f[1600]$ ), assuming that ...
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0answers
75 views

NIST Elliptic Curve Algorithm

I am wondering which algorithms are used to compute ec_mult and ec_twin_mult in the following implementation guidance document. ...
4
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1answer
160 views

I have this list of LibSodium primitives, which should I pick so that the implementations tend to be interoperable?

When I integrate lib sodium, into a c# project, and try to consume, encryption and decryption in a particular way, it works, but the confusion is about, which method to use while encryption or ...
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1answer
136 views

What is an example of elgamal homomorphic double encryption?

I am looking for such an cipher algorithm that is based on assymetric cryptography where the order of encrypting is irrelevant. For example: There is a message "x", Bob encrypt that message with his ...
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2answers
69 views

How does authentication work differently between asymmetric and symmetric cryptography?

Must Bob and Alice establish a 'connection' before a symmetric or asymmetric encryption scheme is secure? If so, is there ever some expected plaintext whose decryption authenticates the users? In ...
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3answers
4k views

Is it possible for a cryptographic algorithm to limit the number of times a package/ciphertext can be decrypted?

I got the idea from Eve Online's BPCs (Blueprint Copy). The in-game explanation is that the license to manufacture a copy of a starship is limited to X times, and afterwards the BPC is automatically ...
3
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2answers
100 views

Figure out algorithm to numeric key generator with one known input and output

I have a software program running on a piece of hardware. To access a specific functionality it runs a challenge-response-like authentication, that is it generates a numerical 4-digit PIN and expects ...
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4answers
943 views

Can SHA or MD5 results be decrypted?

I have learned that SHA-1 and MD5 are one way hash functions, which means that it is not possible to obtain the original value by performing the reverse calculation. There however some online ...
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1answer
66 views

Encrypt 2 numbers preserving arithmetic correlation

I want to encrypt 2 numbers using a public key and have the reader know the correlation between those 2 numbers. I can also share the public key. Example: ...
2
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1answer
83 views

Security of expanded key

Can somebody analyze this scheme and explain how (in?)secure it is? Assume that: The keys were initially securely exchanged All keys are truly random In this scheme: The key size is of length <...