0
votes
0answers
5 views

Disabling CBC ciphers does not stop Chrome from negotiating to use CBC ciphers

I am getting an message about 'obsolete cryptography' from Chrome. Your connection to (site) is encrypted with obsolete cryptography. The connection is encrypted using AES_256_CBC... Per ...
0
votes
0answers
30 views

Can I place a private key on a sim card? [migrated]

After google searching about this idea and yielding very little in results I've come to resort to stack exchange: Is it possible to place a private key on a sim card? Is it possible for a smart ...
0
votes
1answer
30 views

DSA: Authentication and assurance of authorized parties

When dealing with Asymmetric cryptographic algorithms, usually the sender of the critical data asks the listener for a Public Key for encrypting the data and sending them. This is while the private ...
1
vote
1answer
3 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?
0
votes
0answers
5 views

Existence of assumption

Is there an assumption that is of that form: Let an oracle $\mathcal{O(\cdot)}$ on input a message m to output: $g^{k_ix+xym}$ Then the assumption states that is computationally difficult for an ...
0
votes
0answers
7 views

website for cryptanalysis

I was wondering if there's a website that can automatically give information about a text or numerical input to real world data. For example if I give input - 192.167.12.34. It will give WHOIS of IP ...
0
votes
0answers
9 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) ...
2
votes
2answers
56 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 ...
11
votes
2answers
9k views

Calculating RSA private exponent when given public exponent and the modulus factors using extended euclid

When given $p = 5, q = 11, N = 55$ and $e = 17$, I'm trying to compute the RSA private key $d$. I can calculate $\varphi(N) = 40$, but my lecturer then says to use the extended Euclidean algorithm to ...
0
votes
1answer
51 views

anonymous signature implementation and usage?

This is one of the question asked in my class. Implement a anonymous digital signature. So it means hiding signers information. i could not find any article in anonymous digital signing. Also another ...
0
votes
0answers
31 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
1answer
16 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 ...
-1
votes
0answers
11 views

SSL-connection between client and server: how can one make this connection secure?

Suppose a browser C is setting up a SSL-connection with a server S. Then after C has initiated the connection with S by sending a "hello"-message and nonce, S sends back a nonce and a certificate ...
0
votes
0answers
8 views

Gpg4win encryption and decryption issue

A friend and I have a bunch of files that I encrypted stored on google drive. The issue comes up that he can't decrypt anything there. The steps I've taken thus far are 1.) Encrypt the ...
3
votes
2answers
185 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 ...
0
votes
0answers
19 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 ...
1
vote
2answers
65 views

What does ⊕ mean in cryptography?

Can someone please help me with the question below? Explain why 0 ⊕ x ≠ 1 ⊕ x, whatever the value of the bit x. Hence, explain why flipping a bit in the plaintext produces a predictable ...
1
vote
1answer
44 views

Differential Privacy and appropriate noise distribution

In differential privacy solutions and more specifically for queries that they do entail counting the proposed solutions define the laplace distribution that is best calibrated for low error. Other ...
1
vote
1answer
42 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 ...
32
votes
7answers
25k views

Taking advantage of one-time pad key reuse?

Suppose Alice wants to send encryptions (under a one-time pad) of $m_1$ and $m_2$ to Bob over a public channel. Alice and Bob have a shared key $k$; however, both messages are the same length as the ...
-1
votes
0answers
35 views

Find output bit in DES encryption [on hold]

Suppose the input to a round of DES is 1010101010......10101010 (64 bits) and the round key is ...
-2
votes
1answer
45 views

How difficult is homomorphic encryption? [on hold]

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 ...
0
votes
1answer
38 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 ...
0
votes
2answers
158 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 ...
0
votes
1answer
62 views

security proof in pairing based cryptography

Let : $G_{0}$ and $G_{1}$ be two multiplicative cyclic groups of prime order $p$. $g$ is a generator of $G_{0}$ and $e$ is a bilinear map, $e : G0 × G0 → G1.$ $𝐶_{1} = 𝑔^{𝛽𝑠_{1}} $, $ 𝐶_{2} = ...
5
votes
2answers
454 views

Why use randomness in digital signature algorithms?

I understand why randomness has to be employed in encryption, because deterministic ciphers are not IND-CPA. I don't understand why digital signature schemes that employ randomness, like RSA-PSS, are ...
-2
votes
0answers
34 views

Can you undrestand? [on hold]

Can you help me in this protocol what is applied of stage 3 ? $$A\rightarrow{B}\quad:K^A\quad\pmod {P}\\B\rightarrow{A}\quad:K^B\quad\pmod {P}\\ ...
0
votes
1answer
20 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 ...
0
votes
0answers
28 views

Special case of format-preserving encryption

Is there encryption algorithm with the following properties? We always have plaintext in natural language, and the produced ciphertext is also in natural language.
-3
votes
0answers
38 views

Suppose Alice and Bob share a symmetric key K. Consider the following challenge-response protocol: [on hold]

Alice → Bob “I am Alice” Alice ← Bob Encrypt (K,R) Alice → Bob Encrypt(K+1,R + 1) Where Encrypt (K,R) means encrypt the message R with the Key K. Must the challenge R be unpredictable, or is ...
-1
votes
0answers
23 views

RSA : Is finding Public key given Private key as hard as finding Private key given Public key? [duplicate]

The question is quite straightforward : In RSA, is finding Public key given Private key is as hard as finding Private key given Public key? If no, can you explain why?
7
votes
1answer
120 views

Factoring two RSA moduli $N_i=p_i\cdot q_i$ knowing that $p_2=p_1+2$?

It is given two RSA moduli $N_1$ and $N_2$, known to be of the form $N_i=p_i\cdot q_i$, with $p_i$ and $q_i$ unknown primes, and such that $p_2=p_1+2$. Can we make use of that relation to factor the ...
2
votes
1answer
96 views

Is the reduction from left-or-right IND-CPA to real-or-random IND-CPA tight?

A modern trend in cryptography consists of defining security as rigorously as possible, and then designing schemes which are secure according to those definitions. Proving security comes in the form ...
0
votes
1answer
33 views

Question about optimal 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 ...
2
votes
1answer
76 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
0answers
55 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 ...
0
votes
0answers
36 views

Optimisation of AES using JIT and table look ups [on hold]

How can look up tables & JIT Compilation = Just In time Compilation help during optimization of AES?
54
votes
8answers
14k views

How much would it cost in U.S. dollars to brute force a 256 bit key in a year?

I am often told that any key can be broken and that it is only a matter of time and resources for any key to be broken. I know that this it technically true. However, I think that there is probably a ...
0
votes
0answers
45 views

RSA private key confusion [on hold]

I encrypted two letters and I'm trying to decrypt them but it is...weird. the message is: (ma), two letters I change it to it's value to binary according to the ASCII table, and then to decimal. c ...
1
vote
2answers
245 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 ...
1
vote
1answer
240 views

How to verify a shared secret using only AES?

I have two devices that need to verify that they both are in possesion of the same secret key. One of the devices is a very limited embedded device that only has AES128 available, no SHA or other hash ...
2
votes
1answer
118 views

Are well designed crypographic codes unbreakable? (NOT ciphers)

Codes are not to be confused with ciphers. It is known that all known ciphers are theoretically breakable except the one-time pad and this isn't what the question is about. Some cryptographic codes ...
0
votes
1answer
66 views

where can i learn the basics of AES?

i was tasked with making an expo about AES and its steps, but i still cant grasp it, especially when it comes to "key schedule". anyone knows some good material to start learning? or someone can give ...
2
votes
2answers
55 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
0answers
40 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
0answers
23 views

Looking for a Javascript impementation of RFC 5297 (SIV) [on hold]

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) ...
19
votes
4answers
10k views

Should we sign-then-encrypt, or encrypt-then-sign?

We often want to send messages that are both (a) encrypted, so passive attackers can't discover the plaintext of the message, and (b) signed with a private-key digital signature, so active attackers ...
0
votes
0answers
18 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) ...
0
votes
0answers
27 views

Can I submit an encrypted message to see if its breakable here? [migrated]

For some reason I have been thinking a lot about encryption lately. I'm a CS major, but an encryption novice. The skeptic in me feels making a code that uses a fairly simple algorithm would be a lot ...
1
vote
1answer
56 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?

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