1
vote
3answers
57 views

“Strict” software for playing and learning with private and public key

my question is just for teaching/learning practice and I think it's not meaningful for the real world. I've played with openssl a lot but from my understanding it's somehow not strict in the format ...
1
vote
1answer
42 views

Question about discrete log - why can one attacker not solve for g but two colluders can?

I'm reading about the broadcast encryption described in Fiat and Naor's paper, I screen grabbed the relevant part below. My question is essentially: If there's a secret: $g^{abc}$ $mod$ $A$ (where ...
1
vote
1answer
93 views

Bilinear pairing arithmetic

Is this $e(g^x,g^yH^z) = e(g^x,g^y)e(g^x,H^z)$ expression is true? where $ g$ is the generator and $ H \in G $
2
votes
2answers
90 views

Is it hard to recover $p$ from $k \phi(p)$?

Given $k\phi(p)$, is it hard to recover $p$? Here, $p$ is a large prime, $\phi(\cdot)$ is Euler's totient function and $k$ is an unknown integer. Or what's the complexity to recover $p$ from $k ...
4
votes
0answers
72 views

Missing public exponent

Using LUC RSA, I have a list of 8 public keys $(R_1,n_1)$ through $(R_8,n_8)$, and a list of $8$ messages $M_1\dots M_8$. The messages have all been double encrypted. However, one of the public key ...
1
vote
1answer
275 views

How to create a PEM file for storing an RSA key?

I have an RSA private key $\{d,n\}$ and a public key $\{e,n\}$, where $n$ is the modulus, and I also have the prime factors $p$ and $q$ of $n$. I want to create a PEM file containing this ...
2
votes
1answer
163 views

Algorithm for n-of-m keys with partial results

Is there any known and proven algorithm which allows n-of-m keys en/decryption, but doesn't require the keys to be in one location? That is, it allows the plaintext (or ciphertext) to be encrypted (or ...
1
vote
1answer
92 views

Malicious party security model: When one party is corrupted at a time

Consider we have three parties,namely client $A$, client $B$ and a server. Client $B$ and the server can be malicious, but we do not allow the adversary to simultaneously corrupt the server and ...
1
vote
1answer
78 views

Encoding a message to a point of curve y^2=x^3+7 and Bitcoin Core

Where should I look at in Bitcoin Core source code to figure out how the signature process trasform a message in a curve point? To sign a transaction (message) in Bitcoin system, you need to encode ...
0
votes
2answers
201 views

Why does Diffie-Hellman need be a cyclic group?

Why is Diffie-Hellman defined on a cyclic group? Doesn't it work for any commutative operation which the inverse is hard to find? Say Alice and Bob agree in a public prime $c$ and both choose a ...
2
votes
1answer
150 views

Key Check Value standard pratice for asymetric cryptography?

I'm looking for a standard, or sound industry practice, for the equivalent of a Key Check Value, applied to the private key of a public key algorithm, like ECDSA. For DES or 3DES keys, practice (as ...
1
vote
1answer
79 views

Renewing session key

I have a system which (should) never shut down, there are keep alive messages every 30 seconds and normal traffic is very variable, might be a few KB/sec might be nothing more than the keep alive ...
2
votes
0answers
321 views

Proper way to generate symmetric keys [duplicate]

I'm trying to educate my self in key management, how to store them, how to generate them, how to use them properly. I've been trying to find how you would generate a key for symmetric encryption (say ...
2
votes
1answer
87 views

Key derivation design to avoid key leaks

I have the first function that generates keys from AES decryption (128-bit key). It takes seed as input: ...
0
votes
2answers
55 views

Why does spiped use both nonces and ephemeral keys?

Colin Percival's spiped utility uses a pre-shared key and Diffie-Hellman with ephemeral keys to provide forward secrecy. The protocol is summarized in the ...
1
vote
1answer
47 views

The non-interactive proof of verifiable computation: Pinocchio

I am reading the Pinocchio paper. The paper says, in paragraph "polynomial asymptotics" of section 4.2.1, a worker, in order to include $h(s)$ into the proof, has to interpolate $p(x)$, and then ...
1
vote
1answer
117 views

Given an encrypted file, what are possible ways to find its encryption algorithm?

Given an encrypted file, what are possible ways to find its encryption algorithm? Heuristic ways are okay as well.
1
vote
1answer
68 views

What is a good way to handle longer strings using FPE?

While experimenting with this FPE based on FE1 http://botan.randombit.net/manual/fpe.html (well actually a port of it in C#) I found when the string length gets too long (number of characters N) ...
1
vote
1answer
317 views

Is encryption time greater than decryption time?

Is encryption time always greater than decryption time for all encryption techniques (AES / DES / RSA / DNA), or is there a mistake somewhere in my implementation?
8
votes
6answers
360 views

Mutual verification of shared secret

Is it possible to develop a scheme where two parties, unsure if they have the same secret, can verify that the other does or does not share the same secret, without one party being able to cheat and ...
2
votes
0answers
101 views

How to map a handful of numbers in a large range to a much smaller range deterministically without collissions

I want to map a set of long integers (say around 100 different values) that can span the entire 64 bit integer range to a much smaller range such as from 0 to 25000 deterministically with almost zero ...
0
votes
0answers
38 views

Does “identity-based dynamic threshold signature” exist and could such scheme contain a “Signature Combination” algorithm?

I came across [1] and I'm very puzzled by this paper. They use a building block which they call "identity-based dynamic threshold (IBDT) signature", citing paper [2]. First of all [2] does use this ...
4
votes
2answers
334 views

Brute-force attack given small search-space and hash prefix

Suppose we have a value $secret which is a random 56-bit (7-byte) string. Suppose an adversary wishes to discover $secret. The ...
1
vote
1answer
133 views

What is the “Walsh Function” about?

I'm currently dealing on the so called “Walsh Function” (WF) that is written like: $$f^W(a)=\sum_{x\in{F^n_2}}(-1)^{f(x)+(a,x)}$$ What I know is that this function is used to approximate an arbitrary ...
-2
votes
1answer
108 views

How difficult is homomorphic encryption? [closed]

I want to learn more about homomorphic encryption and eventually make a career from it. Currently, I'm thinking to have my bachelor degree in this field. What background should I have for this ? How ...
3
votes
2answers
176 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 ...
1
vote
1answer
236 views

Security proof in pairing based cryptography

Let : $G_{0}$ and $G_{1}$ be two multiplicative cyclic groups of prime order $p$, $g$ be a generator of $G_{0}$ and $e$ be a bilinear map, $e : G_0 \times G_0 → G_1$ and let $𝐶_{1} = ...
1
vote
1answer
171 views

How openssl padding for AES cfb IV?

From a few documents I have read and a few questions about padding here, I think if I passed a encrypted text fewer than BLOCK SIZE, openssl would pad it per PKCS7. And use that padded encrypted text ...
2
votes
1answer
110 views

Defining format-preserving encryption for natural language

Assume we have plaintext in natural language. Can we use format-preserving encryption in such a way that the produced ciphertext cannot be distinguished from natural language?
3
votes
1answer
135 views

What does signed fixed window method mean in ECC?

I am studying (sliding) window method in Elliptic Curve Cryptography (ECC) but I am confused by the term, signed fixed window method. By the way term is used in a research paper and not in the book ...
0
votes
1answer
201 views

Encrypt file name

I'm looking to encrypt (rename) mutiple files name based on a passphrase. Currently the passphrase would be numeric but I can change that to something else if required. I would like to be able to ...
1
vote
2answers
2k views

Is ECB mode safe to use with RSA encryption? [duplicate]

Firstly, bear with me, I'm relatively new to cryptography. In a recent static analysis scan of our application, one of the findings complained that we are using ECB: A mode of operation of a block ...
0
votes
0answers
104 views

How do I prove IND-CPA security of RSA-OAEP?

How do I prove that RSA-OAEP is IND-CPA secure? It would be very good to show how to prove it formally, but an informal proof would also be enough. Because of the random number in RSA-OAEP, RSA gets ...
3
votes
1answer
71 views

Optimal bandwidth cost for Oblivious RAM

Goldreich and Ostrovsky show that any ORAM algorithm must have bandwidth cost $\Omega(logN)$, where $N$ is the total number of blocks outsourced. This is in Theorem C of this paper. But they didn't ...
0
votes
0answers
42 views

trying to get calculator and RSA calculatin does not make sense [duplicate]

got two question, I am novice in the area of crypto and currently in big learning curve. From crypto book I am going over with, I see the RSA algorithm example as follows: it chose two rand #-s: ...
0
votes
1answer
313 views

Where can I learn the basics of AES?

I was tasked with making an expo about AES and its steps, but I still can't grasp it, especially when it comes to "key schedule". Does anyone know some good material to start learning? Or can someone ...
0
votes
0answers
21 views

RFC 5297 implementation [duplicate]

I am looking for an implementation of RFC 5297 algorithm using javascript. I would like to see how to wrap a key on client side web browser, like Mozilla's fxa-auth-client (That uses a xor to wrap) ...
1
vote
1answer
117 views

How to decrypt unusual Many Time Pad

How does one decrypt the many time pad: ($R$ is a random string, $C$ is ciphertext, $P$ is plaintext) $R_0 \oplus R_1 = C_0$ $R_2 \oplus R_1 = C_1$ $P_0 \oplus R_1 = C_2$ assuming that $R_n$ are ...
2
votes
0answers
128 views

Simplicity and precision in cryptography papers [closed]

I know a PhD student who recently had his paper on applied cryptography rejected because one the reviewers claimed that it was "the solution was too simple and the notation used was more than ...
2
votes
0answers
65 views

Energy necessary for brute-forcing or decryption

I am trying to understand how the physical limits of computation apply to crytography, and came up with the scenario below as a sort of gedanken. I would be grateful to see how others answer it. ...
0
votes
0answers
47 views

Decypting a Stream Cipher

I am trying to decrypt a stream cipher. I know what the first word of the message is when decrypted but I am unsure how to decrpyt the rest of the message. I know what the first word is because I ...
1
vote
1answer
176 views

Clefia Vs AES 128 bit

I am running a comparison between Clefia (Lightweight cipher from Sony Corporation which is a standard now http://www.sony.net/Products/cryptography/clefia/standard/index.html) and AES 128 bit. The ...
2
votes
1answer
127 views

Format preserving encryption FFX

In FFX mode the format of the ciphertext is same as plaintext. How does it ensure data integrity and authentication? Is there any bit flip attack in FFX mode? Is it malleable?
2
votes
1answer
92 views

Does SipHash have 64 bit (second) preimage security?

I was not able to find an explicit statement about the first and second preimage security of SipHash-2-4 or SipHash-4-8 anywhere. I think it should be 64 bits, but I'd feel safer if somebody who has ...
0
votes
1answer
74 views

Is it a bad idea to use PGP encryption for structured/predictable data?

I'm working on an app and need to encrypt some structured data. The data will be turned into a string form (JSON) before getting encrypted. The data format I'm using will always start with a ...
1
vote
2answers
182 views

Are there any quantum-resistant symmetric encryption schemes?

It seems that quite a few currently available encryption schemes will possibly be broken by quantum computing. Are there any symmetric encryption schemes that will remain unbroken (either because of ...
0
votes
0answers
35 views

Does Windows CNG store private information using LSA secrets?

I read that LSA Secrets have the capability of storing data privately, more importantly, ensuring that users without proper permissions cannot access that same data. Windows CNG has security measure ...
2
votes
2answers
547 views

PGP digital signature vs SHA256 HMAC Comparison

First let me admit that I am not a mathematician or a cryptographer. I am responsible for assisting in making a recommendation on a project that is consolidating payment processes within a company's ...
0
votes
1answer
77 views

How to select a 'tweak' used in FE1 mode format preserving encryption?

I'm experimenting with this library Botan which includes a module for format preserving encryption based on FE1 mode. The parameters for the Encrypt method are as follows ...
0
votes
0answers
49 views

What is sLHAE (stateful length-hiding authenticated encryption)?

Can somebody please explaint me how does sLHAE works in TLS? I met this term in some TLS papers and struggled to understand how it works, specifically the "length-hiding" part.As to my understanding ...

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