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How to forge a signature in a custom PMAC implementation

From a crypto challenge i have the following PMAC variant where the task is to forge a signature to fulfil a specific condition: Preparation: in the finite Field GF(2^128) with the polynomial x^128 + ...
-2
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0answers
14 views

Can anyone help me with this code? Related to Base64 Encoding [closed]

3qqIPPNX0fxjJv/krWhw7L8P83cTm2Dm2aOHHiAfNZQG1Q/1t1zPaY7CEwZBrHIC I am guessing it is base64 encoded, however base64 decoding won't work on it. I can't figure out how to solve it.
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0answers
8 views

Using the output of HKDF directly

I am using HKDF with an IKM and salt, the OKM is used as the key for an HMAC operation. The HMAC algorithm is authenticating messages in a communications system The salt is the concatenation of 2 ...
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0answers
10 views

LSIM library based on LibScarab

In a book called: "Intelligent,Secure and Dependable Systems in Distributed and Cloud Systems" where we can find some of its pages on the following URL: https://books.google.com.lb/books?id=...
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15 views

Cipher Block chaining but with encrypting the plain text first then xor with IV

I have just learned about the CBC mode of operation and that it gives the cipher by xoring the plaintext m0 with random IV and then encrypt it with random key and I found out that the CBC is not CPA-...
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1answer
27 views

using 0 nonce for AES-CTR

so, the question is: will it be less secure if I use a random key and static zero nonce? key = random; nonce = 0;
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0answers
11 views

A variant of LPN problem

I have a question regarding the LPN problem. The search LPN problem is to find $s$ given $(A,As+e)$ I am thinking about another problem that given $(A,As+e,As'+e',s+s')$ to find $s$, where $A$ is a ...
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0answers
31 views

why Java does not support KMAC algorithm out of the box? [closed]

My question seems specific for Java since I am looking for KMAC generation in JVM. Java runtime currently supports HMAC code generation. why is there no support for KMAC out of the box? Any standard ...
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0answers
16 views

Calculate the complexity of HKDF with a 96bit salt and a 128bit key?

I have a 128bit PreSharedKey. I don't want to use it directly. I'd much rather generated a session key with HKDF + PSK + SALT = SESSIONKEY. But... I'm under strict size limits for packet size. So I'm ...
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15 views

Three Pass Protocol Question!

Alice and Bob have agreed to use the Three Pass Protocol. p=1009 Alice chooses the encryption exponent e_A = 101 Bob chooses the encryption exponent e_B = 209 Now Alice and Bob send three ...
2
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1answer
71 views

ChaCha20: Can my salt/pass for a KDF also be the nonce?

I have a PSK. I don't want to use it directly. I want to pass a "salt"/password into a KDF and get a new key. I need to give the other side the nonce used. I don't have enough space to fit all of ...
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19 views

Secure File Transfer with Individual Control

I am pretty much a newbie in this field, but I have been searching for an answer last 4 hours, without break. So I wanted to type it on here. My main goal is to build Raspberry Pi cloud storage and I ...
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0answers
22 views

Using PSK starting a new session, encrypt the new session key with old, or sign a derivative to be used on the old key?

I have two endpoints that go through a middleman. Both have a pre-shared and secure key, 16bytes to be used with ChaCha20-Poly1305. Extremely constrained device. No packet larger than 100 bytes total. ...
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0answers
13 views

How does a rectilinear filter used for QKD-BB84 detect both horizontal and vertical polarizations?

When using the BB84 algorithm for QKD, you arbitrarily choose which of two filters (bases) to use when detecting a photon: rectilinear or diagonal. If you choose rectilinear, you can detect ...
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19 views

How is QKD (Quantum Key Distribution) advantageous over McEliece/AES?

I don't understand the popularity of the idea of QKD (often coupled with OTP). From what I can tell, a quantum-safe key exchange algorithm like McEliece has just as much security while being able to ...
2
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2answers
88 views

Diffie-Hellman in Https: How are prime numbers picked?

I am trying to understand https, as I understand https uses the Diffie–Hellman method for keys exchange and then AES for encryption. But Diffie–Hellman needs two prime numbers, where do these come ...
2
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0answers
13 views

Does the size of data to be encrypted influence the security of Gmac?

In this link: Has GMAC mode a future outside GCM?, the last comment given by the user Demi, indicates that the larger the size of the text to be encrypted, the lower the security of the gmac. Why is ...
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8 views

XTZ Private Key

The BIP39/44 off-line tool does not contain XTZ coin. Therefore, I cannot derive (from my 24 words) my ledger nano s private key associated with my Public key for my Tezos account. Is there another ...
1
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1answer
50 views

Why GCM operation mode with AES-128 is recomended and can we use AES-192 and AES-256 with GCM?

It happens that on the internet I often find that AES encryption should use a 128-bit key only if it is used in conjunction with the GCM mode of operation. Why only with 128-bit keys? What happens ...
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0answers
9 views

TDES(Triple DES) DUKPT decryption

We have a POS(Ingenico) that uses DES3_CBC encryption using a derived key. It sends encrypted data, and 10 bytes size KSN. I tried to use CKM_DES3_CBC_ENCRYPT_DATA to derive the key, and decrypted the ...
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0answers
22 views

Are there any algorithms for which generating any zero-knowledge proofs is not practical?

It is related to my earlier question: Can zkSNARK or other zero-knowledge proofs be used to proof message authenticity without revealing private key? Are there any algorithms for which generating ...
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0answers
15 views

Repeatable encryption for pseudonymisation

Is there a good way to do repeatable (with the same result) encryption for pseudonymisation where the pseudonym can be decrypted? I want to set up a system to allow multiple services to communicate ...
1
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0answers
34 views

Security of ECC over finite fields of characteristic $p\approx2^{50\pm10}$?

What's the security of Elliptic Curve Cryptography over finite fields of word-sized characteristic $p\approx2^{50\pm10}$? We are talking about $\Bbb F_q$ where $q=p^k$ for some suitable $k$. ...
1
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2answers
79 views

multiplicative inverse [duplicate]

I actually do want to know how to generate the multiplication inverse (M.I) table, I mean the calculation how the M.I been generated.. such as the M.I of 22 is 5A regarding to the table.. Do you know ...
2
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2answers
36 views

Mathematical definition of deterministic and non-deterministic random bit generators

Can anyone give the mathematical definition of deterministic and non-deterministic random bit generator? Providing a reference will also be very helpful.
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0answers
15 views

How to find/determine the Polybius Square Key and Additive Key, if only the Cipher Text is known, in Nihilist Cipher?

I was solving a Crypto Challenge in a CTF, and I got a Nihilist Cipher Encoded String. Luckily the additive key was given as a hint, and for the polybius Square key, I kinda bruteforced or I just got ...
0
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1answer
32 views

Length extension attacks, Merkle–Damgård constructions, and HMACs

The wikipedia page for Length Extension Attacks says "Note that since HMAC doesn't use [Merkle–Damgård constructions], HMAC hashes are not prone to length extension attacks." However, HMACs can be ...
0
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1answer
45 views

Discrete log problem exponential runtime

I am trying to understand the runtime complexity of the discrete log problem (in the most basic sense). So, if we have $\langle g \rangle = G$ and are trying to find $g^x = a, a \in G, 0 < x < ...
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0answers
65 views

How to reverse this simple xor encryption function? [closed]

this code decrypts encrypted rom code from an arcade game pcb (it is from source code of Mame emulator) for each byte in rom... ...
1
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0answers
42 views

Help on Algebraic Side Channel Attacks

I am a master student in computer security, I am preparing a dissertation thesis in the theme is: Algebraic cryptanalys by auxiliary channels, I need reference on this theme (book, thesis, ...), and ...
1
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1answer
55 views

Can quantum algorithms solve the approximate GCD hard problem efficiently?

Some cryptographic schemes are based on the hardness of this problem. The answer to this question determines if those schemes are quantum resistant or not. There are a number similar questions but ...
3
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1answer
111 views

Is this a PRF? Fk(x) = G(k⊕x) where G is a PRG

This is not homework, but a random thought. Let $G(x)$ be a PRG. We define the following function: $$F_k(x) = G(k\oplus x)$$ My intuition is that it shouldn't be a PRF but I couldn't come with an ...
1
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0answers
36 views

Game-based proofs and semantic security

After reading this question, I understood that "game-based" and "simulation-based" have to do with the way that security properties are postulated. In particular, IND-CPA is a canonical example of ...
0
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1answer
26 views

Publicly verifiable secret sharing scheme

In https://www.win.tue.nl/~berry/papers/crypto99.pdf, Schoenmakers proposes a publicly verifiable secret sharing scheme, that uses a non-interactive DLEQ proof to allow any participant to verify the ...
1
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0answers
30 views

where are ssh.com's crypticore and seed defined?

ssh.com's Tectia offers a few algorithms seemingly unique to itself. Chief among them: crypticore128@ssh.com, crypticore-mac@ssh.com and seed-cbc@ssh.com Are these algorithms publicly defined ...
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0answers
34 views

Discrete log zero knowledge proof lying case

I read the Wikipedia page on a discrete log zkp, but I don't understand how $$C' = g^{r'} \cdot (g^x)^{-1} \bmod p$$ would be calculated. Would it be $$C' = g^{r} \cdot \frac{1}{y} \bmod p$$ ...
1
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0answers
40 views

Bilinear Map over RSA group

Is it possible to build a bilinear map where the underlying group is an RSA group? I.e. $e: \mathbb{Z}_N \times \mathbb{Z}_N \rightarrow \mathbb{Z}_N$ where N is an RSA modulo? Alternatively, a ...
1
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1answer
24 views

Binary verification of application image before loading it into DRAM

Working on a boot process where the application image has to be verified before loading it into DRAM. We found 2 strategies; RSA-1024, where the private key is secure in premises and the only public ...
1
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1answer
37 views

Compute statistical distance between two distributions over tuples

Let $X$ denote one distribution. Let $f,g, \text{ and } h$ denote three functions. If we have the results: $g(X)$ is within a negligible statistical distance of $h(X)$. Is it possible to prove $$(f(...
1
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1answer
53 views

Is there any practical use of reduced rounds of AES

There are lots of attacks which are on reduced block ciphers. There are practical attack on five rounds of AES-128five rounds aes broken in six minutes. I was just wondering if there is any practical ...
1
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0answers
20 views

Can a fuzzy hash be used as a less accurate merkle root?

If I had many, say a million random numbers (technically public keys.. ~600 bytes each) and I wanted to hash them all together using a fuzzy hash, how accurately could I test that a given hash was a ...
2
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1answer
49 views

Randomness of Decision Learning With Error Problem

I read the statement of the Decision Learning with error problem is: distinguish between $(\vec a, \langle \vec a, \vec s \rangle + e)$ from uniformly random samples. Can anyone explain what does ...
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0answers
29 views

Prove that for key with $n$ dimensions, the order of the key is $k!$

I need to prove, that for a key with $n$ dimensions, they order of the key would be $n!$ and to prove that, I need to use mathematical induction: $$\text{Let n = 1} \Rightarrow {1} \text{ if there ...
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0answers
42 views

Trying to understand how the same secret key end up being calculated between Alice and Bob

This is basically a duplicate of this question which was not answered very clearly. From the documentation, these are the calculations that happen for Alice to compute the shared secret key: ...
0
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0answers
44 views

Elliptic Curve - X Coordinate

I am currently working on a Koblitz curve. I have found the curve has two matching groups based on the base curve point and N-1 point. My question is as follows: Is there an algorithm to determine how ...
1
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0answers
48 views

Store symmetrical (AES) key in Indexeddb?

Using web crypto API and it won't let me store an AES key in the indexeddb (it requires a public/private key). Does anyone have suggestions on how to do this? Should I/could I create a public/private ...
0
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0answers
30 views

Can zkSNARK or other zero-knowledge proofs be used to proof message authenticity without revealing private key?

The situation: Alice and Bob are exchanging messages encrypted by some known asymmetric encryption protocol. All their encrypted messages, as well as public keys are intercepted by Charlie. Can ...
0
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1answer
94 views

Factorization problem

Say, $X= a\cdot b$, where $(a, b) \in Z_q^*$ and $q$ is a large prime. If $X$ is given, then what is the complexity (or hardness) of finding $a$ and $b$? Note that, either $a$ or $b$ can be reused to ...
2
votes
1answer
64 views

Why is there no “ephemeral non-DH EC” key exchange in TLS?

In RSA key exchange, the client picks a premaster secret and encrypts it with the RSA public key in the server certificate, and sends it to the server. This offers no forward secrecy. In ECDHE key ...
3
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1answer
175 views

Is this problem on $\mathbb{Z}_p$ really hard?

I just want to know if there's something obvious that renders this hard problem useless. Not a full cryptoanalisys. Any hint on whatever is welcomed. We will work with the Ring $\mathbb{Z}_{p}$, $p$ ...

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