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96 views

Is it possible to truncate AES output and keep uniqueness (no decryption needed)? [duplicate]

I would like to hash numbers less than 1000000000, so generally they could be stored on 30 bits. The aim is to obtain numbers that are not reversible, so my initial plan was to use SHA256 (with some ...
2
votes
1answer
103 views

How strong is XooDoo vs AES?

What is Gimli, and how does XooDoo compare to symmetric ciphers such as AES or ChaCha? I am looking at this library, called charm. Interesting paper here. I also ...
-1
votes
1answer
72 views

Is that possible to calculate modular inverse of a point on elliptic curves?

Imagine that you are given a point $P$ so that $P=a\times G$. If you have no knowledge of $a$ is that possible to calculate point $I$ so that $I$ is the modular inverse of $P$? We know that over ...
-1
votes
0answers
44 views

Fully homomorphic encryption noise reduction using modulus switching technique

Let we have the following encryption scheme such that, Encryption: $$C = m + r p^q \mod n$$ Where $n=p*q$ and $q, p>q$ are two large prime numbers as the private keys. Also, $n$ is the public key....
1
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0answers
55 views

How to sign comitted group elements?

I'm actually searching some particular primitive compatible with Groth Sahai commitment. I would like to know a signature scheme (on group elements), such that there exists an algorithm $\mathtt{...
3
votes
3answers
197 views

Most secure but feasible encryption running on WWII technology

Imagine you are transported back to ~1940. What is the best (i.e. most secure, but technologically feasible) encryption you can think of for widespread (i.e. military) use? How would you implement it?
0
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0answers
38 views

Pairing-free group based encryption scheme

Can someone explain what is a pairing-free group ? There is encryption schemes, for example 1, that qualify there proposed construction as pairing-free group. However, they use bilinear group in the ...
1
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0answers
23 views

How can blockchain ensure uniqueness of a digital asset like a photograph?

If I take a picture with my beloved camera, the RAW file can be put into a blockchain, and thus it will have a unique hash. If that unique hash is ever spotted anywhere we know it's a copy of my ...
0
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0answers
33 views

How TAU function of SM4ni cipher is implemented?

I am trying to understand the SIMD implementation of TAU function of SM4 which is as follows: ...
1
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0answers
33 views

Is it possible to enhance white-box cryptography security by homomorphic encryption?

Background: Let's discussed based on published symmetric white-box crypto only, such as Chow's white-box AES. I only know basic concepts/objectives of homomorphic encryption, such as PHE and FHE. ...
7
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0answers
118 views

Why is BLAKE2 faster than chacha20?

Chacha20 is essentially a hash function that maps 512-bit strings to other 512-bit strings which are in turn xored with the plaintext to create the ciphertext. Of the 512-bit input 128-bit are used ...
1
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1answer
44 views

Hill Cipher Plaintext Attack: Dealing with Non-uniqueness of Matrix Inverses?

I'm following along with my book. Here is an example of a plaintext attack from it: It is known that: plaintext = 'friday' ciphertext= 'pqcfku' $m$ = 2 We will use this to form the following matrix ...
1
vote
1answer
31 views

Side-channel resistant discrete uniform sampling on $d\neq 2^t$ values?

Assume you have some source of $\mathsf{Bern}(1/2)$'s (probably some CSPRNG in practice). What is generally done to sample from $\mathsf{Unif}([d])$ in a side-channel resistant way (assuming $d$ isn't ...
6
votes
0answers
91 views

Rationale for NORX/Ketje/Keyak not being chosen for the CAESAR final portfolio

Was any specific rationale given on why none of the sponge-based AEAD algorithms (specifically NORX, Keyak, and Ketje) of the 3rd round candidates of the CAESAR competition made it to the final ...
0
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0answers
26 views

Pitfalls of wildcard certificates with unique key pairs?

I am having difficulty finding information regarding using wildcard certificates with unique key pairs. I understand if you duplicate key pairs across multiple servers and one becomes compromised, an ...
1
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0answers
26 views

Asymetric encryption, multiple recipients, traitor must share private key

Is there an Asymetric encryption scheme, or public key encryption, where multiple recipients are able to access the data but in order for one of the recipients to leak the key to the data they would ...
0
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0answers
13 views

ChaCha20-Poly1305 calculates wrong mac [migrated]

Currently I have built an application for Android and PHP which encrypts some data using chacha20-poly1305. Those are working fine since I am using libsodium as their backbone. However, now I have ...
2
votes
1answer
88 views

Is there any asymmetric encryption algorithm for eliptic curve(secp256k1) without AES? [duplicate]

I am looking for asymmetric encryption using SECP256K1. But all over the internet, I see that it also requires AES encryption. Instead of generating an AES secret key, is it possible to encrypt using ...
1
vote
1answer
56 views

AEAD without explicit authentication tag

I'm trying to understand the purpose of tag in AEAD. As far as I can understand, the resulting ciphertext will be slightly longer than the plaintext due to the authentication tag. Will it reduce the ...
0
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0answers
5 views

Unable to decrypt aes-192-gcm [migrated]

I'm using nodejs to encrypt and decrypt aes-192-gcm here's my code: ...
2
votes
1answer
44 views

Where does signing/decrypting take place on a YubiKey 4/5 PIV private key?

I have a YubiKey 4 and want to use it to store a private key that should never enter a computer system's memory. After importing the key to the device I understand it never leaves it. Do the signing/...
3
votes
1answer
107 views

Please explain me why we require $2^m$ & $2^{\frac{m}{2}}$ random messages

Assume that a one-way Hash function is secure and the best way to attack it is by using the brute force attack. It produces an $m$-bit output. Finding a message that hashes to a given hash value would ...
0
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0answers
23 views

Should i hash or encrpt the data first? Why? [duplicate]

Lets say alice is trying to send data to bob , should alice first hash the data and then encrpt or vice versa
2
votes
0answers
36 views

Recover secret SHA-1 constants given Oracle

There's a black box that's basically SHA-1, except that the constants (h0, h1,...,h4) are secret. We can pass it arbitrary inputs and get the corresponding outputs. Given this, is it possible to ...
7
votes
2answers
548 views

When encrypting twice with two separate keys, can a single key decrypt both steps?

Is it possible that if a plaintext is encrypted first with a key, $n_1$, and then this ciphertext is again encrypted using the same algorithm but a different key, $n_2$ that the resulting ciphertext ...
0
votes
1answer
50 views

Does every language's SHA256 implementation provide different result for the same value [duplicate]

Probably this is very naive question, based on lack of understanding but I was watching a video from Andreas M. Antonopoulos about blockchain, bitcoin and consensus algorithms and he asked for the SHA-...
2
votes
1answer
33 views

Recommended key size for DKIM

What is the recommended key length for DKIM? I'm currently thinking about a 1024-bit key vs. a 2048-bit one. From the crypto point of view for RSA, 2048 or 4096 bits is clearly recommended--no ...
2
votes
0answers
81 views

A proposal for randomization of Niederreiter cryptosystem

The Niederreiter cryptosystem is a public key cryptosystem using Goppa code. Unfortunately it it is insecure unless it is a binary code. So I thought I could insert random linear codes into randomly ...
1
vote
1answer
26 views

Multiple rounds of (Committed) Oblivious Transfer

I would like to know a protocol which computes the following functionality: Alice chooses a bit b. For i = 1 to n, Bob chooses $x^i_0$ and $x^i_1$. For i = 1 to n, Alice and Bob run $F_{OT}$ with ...
1
vote
1answer
39 views

Looking for a formula for “Given $x_1$, $\ldots$, $x_{n-1}$, the output $F(x_1,\ldots,x_n)$ is dependent of $x_n$ and is of $l$-bits security”

Suppose I have a function $F(x_1,\ldots,x_n)$, where each $x_i$ is of $l$-bits security (suppose each $x_i$ is a binary string of length $l$). At the same time, suppose there are $n$ persons, each one ...
0
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0answers
5 views

Where is the AES-256 key/ IV pair stored in wallet.dat file? [migrated]

I have created an encrypted bitcoin file. I know the password and I see the mkey in the hex dump. I would like to know where the AES key / IV pair are located in the wallet.dat file?
-2
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1answer
68 views

Is permutation conjugate search problem many answer? Are there many answer equal? [on hold]

If conjugate search problem of permutation is difficult , then there are next cryptosystem will appear. A=XYX−1,B=XZX−1,Y and Z are public key.And X is secret permutation. then encryption is C=...
2
votes
1answer
74 views

Transfer and hide ciphertext with hash functions?

Can hash functions be used to transfer and hide ciphertext? This somewhat similar locked question, "If cryptographic hashes are completely unique, could they theoretically be used to transfer data?", ...
3
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0answers
39 views

Small(er)-lane Keccak-f: impact and usage

Keccak defines a family of hash functions, by building a sponge out of a permutation Keccak-$f[b]: \{0,1\}^b \rightarrow \{0,1\}^b$. This permutation function is parametrised using $b$, which is the ...
0
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0answers
18 views

Which SHA-1 attacks apply to TOTP tokens? [duplicate]

Update: it's actually hmac(secret, time). I'll leave the post as-is, in case someone is ever looking for the hash(secret+time) ...
0
votes
0answers
9 views

Is it really required to encrypt files explicitly our self knowing that S3 will keep everything encrypted? [migrated]

As AWS S3 already keeps files encrypted. What could be the use case where we need to encrypt our file using any other library explicitly. Is that required in real world application ? Is it really ...
1
vote
1answer
65 views

AES256 key entropy requirements

Is this encryption method sensitive to weak keys? Is there any reference in the NIST on the AES key's entropy? (For example, must it have been generated from a TRNG?) Can I safely use the Microsoft ...
1
vote
0answers
20 views

how to measure/calculate guessing entropy for side channel attacks

I was going through the paper (https://link.springer.com/chapter/10.1007/978-3-319-66787-4_3), and I came across where authors says that accuracy alone is not enough as an evaluation metric and ...
1
vote
2answers
53 views

Very short block ciphers for equally-short plaintexts

I'm trying to develop an encryption technique for encrypting short phrases (such as reversibly-anonymized names) in text. The key-generation and ciphertext-representation details are fungible, but ...
5
votes
1answer
79 views

Blum Blum Shub Pseudo-Random Generator Requirements

I am trying to understand the Blum Blum Shub pseudo-random generator originally described in A Simple Unpredictable Pseudo-random Number Generator As best I can tell the requirements are: For any $...
3
votes
2answers
44 views

What's the meaning of probabilities in differential privacy formula?

I don't understand what does it mean by "The probability is taken is over the coin tosses of K." Does it mean, the probability distribution is generated based on exactly same data but only the ...
0
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0answers
32 views

ECDSA dA multiplication algorithm [duplicate]

I was looking at this question and i can`t understand this part: QA = dA G = 5 (5,1) = (9,16) I saw that algorithm used for this was Double-and-add algorithm but i didn't get it. Can ...
1
vote
1answer
75 views

Can the person who decrypts a homomorphically encrypted value know what operations were run?

I'm looking at the SEAL library but I'm trying to figure out what happens in a certain use case. For example: Alice encrypts the number 123456 homomorphically and sends it to Bob. Bob adds 25 and ...
0
votes
0answers
17 views

Using PIN to enable MFA for YubiKey-based logon provider

I've created a custom credential provider (for Windows) that allows logon just by inserting a YubiKey. The user's Windows password is protected as follows: ...
2
votes
2answers
88 views

Talking TLS with EC cryptography and the secp256k1 curve [duplicate]

How reasonable would it be to speak TLS over the secp256k1 curve? My initial experiments show that OpenSSL supports it (albeit with special flags, see below): Running an OpenSSL client against an ...
0
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0answers
11 views

is it safe to AES encrypt the RSA private key and storing it in the database [migrated]

i'm building an app that really needs encryption of this type , my question is it safe to store the aes encrypted RSA key in the database ? here is how i encrypt the key : i generate a random 256 ...
1
vote
2answers
91 views

From the product of two permutation matrices raised to the same power, is it easy to find the power?

Let $A$ and $B$ be two public permutation matrices. If $r$ is a secret power of large number, can we easily find $r$ from $A^rB^r$?
4
votes
2answers
547 views

ECDSA: Why is SigningKey shorter than VerifyingKey

Total Crypto Noob here. I was wondering why in ECDSA the Signing Key is so much (half of) shorter than the Verifying key? Lets look at some python code: ...
3
votes
2answers
196 views

How can the 'randomness' of a finite sample of binary keys from a finite key space be estimated?

Given a set of bit sequences generated by an extractor, what would be a valid setting for estimating the randomness of these generated keys and what resolutions can be drawn for that extractor in ...
0
votes
1answer
107 views

Is Permutation conjugate problem hard?

Let $x$,$y$,$z$ be permutations. Then public key is $z=xyx^{−1}$ and $y$. Is permutation conjugate search problem easy? if yes, how to find $x$ from $z$ and $y$? Let be a is Alice's secret key as ...

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