-1
votes
1answer
131 views

Decrypted RSA 64 bit encryption using modulus and private exponent. Got gobbledygook [Verify] [closed]

As part of an experiment, I was given a .enc RSA (encrypted) file that was most likely generated using openssl. I had the public key, I factored it, obtained the private exponent, and decrypted the ...
2
votes
1answer
127 views

Hash functions to the power of two and three notation

I have found in a Wireless Sensor Networks security paper, operations where cryptographic hash functions are elevated to the power of 2 and to the power of 3 (i.e. $h^2(x)$ and $h^3(x)$). This might ...
2
votes
0answers
62 views

Pseudorandom Function Proof

Given a set of pseudorandom functions $F=\{f_s^i\}_i$ for each $s\leftarrow\{0,1\}^n$ generated at random; moreover each $f_s^i$ uses a specific PRG $G^i:\{0,1\}^n\to\{0,1\}^{2n}$, where: ...
0
votes
1answer
48 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
1answer
175 views

How to decrypt a '.enc' file that has been encrypted with RSA using a public key? [closed]

While solving a CTF challenge online, I came across a situation where I needed to decrypt a '.enc' file that has been encrypted using someone's public key. The ...
0
votes
1answer
41 views

What is the difference between chosen-plaintext attack and adaptive-chosen-plaintext attack?

I've just dived in cryptography and would like to learn basics of this science. Currently I can't understand the difference between these two types of attacks. As I understood from Bruce Schneier's ...
0
votes
1answer
29 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 ...
0
votes
1answer
36 views

Identification by RSA

Suppose we have identification scheme as such: Bob takes random $r$, and encrypts it with Alices public RSA key $(n,e)$, sends $r^e$ to Alice. Alice decrypts $r$ and sends it back to Bob, becomes ...
0
votes
2answers
107 views

Removing “security by obscurity” from port knocking

Every article about port knocking, for instance https://wiki.archlinux.org/index.php/Port_Knocking , declares this method as security by obscurity. Is the following enough to remove that title; a ...
1
vote
1answer
38 views

Replay Attack in Stream Cipher

Stream ciphers are vulnerable to replay attack if the same key k is used. If E() is a stream cipher and an attacker intercepts the message m that's being transmitted at time t, how can the attacker ...
0
votes
0answers
25 views

For intrusion detection, tripwire, using crypto hash integrity checking - what can be expected? [migrated]

Intrusion detection using something like Tripwire that conducts integrity checks through crypto'ed hash functions of files requires a scan and to hash the file and save this for later comparison. ...
1
vote
1answer
64 views

What is the purpose of pre master secret in SSL/TLS?

I studied about SSL/TLS and learned that client and server must share keys below. common key for encryption common key for generating message authentication code Then, in SSL/TLS, a client doesn't ...
1
vote
1answer
72 views

Will ANY prior knowledge assist in determining contents of a SHA1 hash?

I am working on a project testing a hash that protects some data, and I've already eliminated hash length extension attacks as a possible point of compromise, and I'm trying to educate myself on all ...
1
vote
1answer
88 views

Solve a problem, thought it was hash length extension, hours later, am I wrong?

Here is my situation. I'm working with an application for which uses hashing to authenticate data. I have a string, which is hashed. It is, like in a hash length extension attack, H(key:known_value) ...
0
votes
3answers
81 views

Is the keystream transmitted with the ciphertext when a stream cipher is used?

When a stream cipher is used and a keystream is generated to be XOR'ed with the plaintext, is the keystream sent with the ciphertext so that the receiver knows how to decrypt it? Or does the ...
5
votes
1answer
148 views

Crack linear congruential generator knowing every other word in sequence

I need to crack one of the example of linear congruential generator. I have $X_{n+1} = (a \cdot X_n + b) \bmod m$ and I know every other word in the output sequence: ..., 3158, ..., 1888, ..., ...
0
votes
1answer
79 views

Required key size for an ideal cipher with a 32 bit block size

For an ideal block cipher, what size key would be required when the cipher has a 32-bit block size?
1
vote
1answer
110 views

Is there a need to encrypt data when send over https? [closed]

I was monitoring web traffic from my Android mobile using Man in the middle proxy. I installed certificate signed from my server in my mobile and I could see all applications sending sensitive ...
0
votes
1answer
53 views

Will there always be 256 collisions for the output of the MD5 hashsum function for 17-byte inputs?

By my math, if you are inputting all possible 17 byte values, and the output is 16 bytes long, then there must always be 256 possible inputs that will result in each output hashsum. However, looking ...
1
vote
1answer
77 views

What's the differences among Blind Computation, Secure Multi-Party Computation, Secure Circuit Evaluation and Homomorphic Encryption

We know that Blind Computation, Secure Multi-Party Computation, Secure Circuit Evaluation and Homomorphic Encryption all can process the encrypted data, but I am puzzled by them. What are their ...
1
vote
1answer
74 views

Are there any valid, and person readable, checksums possible?

We've been trying to produce a valid, and pretty, MD5. Something that has repeating digits, or spells a word, or something. It's probably more difficult than spelling out the dictionary on a ...
1
vote
0answers
73 views

In what countries am I now allowed to talk about technical details of cryptography? [closed]

I hope this is the correct place to post this, otherwise I'm sorry. The OpenSSL Legality section states: OR EVEN JUST COMMUNICATING TECHNICAL DETAILS ABOUT CRYPTOGRAPHY SOFTWARE IS ILLEGAL IN ...
1
vote
3answers
66 views

Decrypt AES-encrypted data with another key

Here is a plain question, all filled with pseudo-real data :) We have a string: "hello" and two keys for AES: GoodKey and BadKey. We encrypt our string with GoodKey, and receive something like ...
0
votes
1answer
81 views

What makes this mixer function resistant to differential cryptanalysis?

I recently learned how differential cryptanalysis works, and decided to have a play around with testing various designs for resistance against attack. My testing algorithm is essentially to loop ...
1
vote
1answer
100 views

How to encypt/decrypt messages after ECDH key agreement

I am using Diffie-Helman key exchange to generate the shared secret. But how will can a message be encrypted using this shared key?
0
votes
1answer
53 views

New to cryptology, studying key exchange

I'm just getting an overview of some of the concepts in key exchanging at the moment, and I'm a bit disoriented on a few topics, namely key stretching, key derivation functions and perfect forward ...
0
votes
1answer
45 views

uniform vs. non-uniform PPT

I'm trying to understand PPT and in particular what the differences are in uniform and non-uniform PPT's. First, this is how I see it: A Probabilistic Polynomial-Time algorithm A is an algorithm that ...
0
votes
1answer
41 views

Probability of SHA256 Collisions for Certain Amount of Hashed Values

I wonder if you can help me figure out that question: Is there a known probability function f: N -> [0,1], that computes the probability of a sha256 collision for a certain amount of values to be ...
1
vote
1answer
47 views

Average/approximate difference in value between valid consecutive $x$ coordinates in ECC?

From my basic understanding not all values of $x$ coordinates can satisfy a given elliptic curve equation, i.e. some $x$ coordinate values are not valid points on the curve because $x^3+ax+b$ is not a ...
3
votes
1answer
349 views

What are the vulnerabilities of this homemade encryption algorithm?

I decided to program a relatively trivial encryption algorithm in my downtime. This algorithm takes a seed from a user (supports floating point seeds), and then adds 1 to the seed for every iteration ...
0
votes
0answers
31 views

Vigenère + columnar transposition

I'm trying to decode a text which is encoded by Vigenère followed by a columnar transposition. The method I want to use is trying random columnar transpositions and then rating how much the text that ...
0
votes
0answers
35 views

Recover keys using statistical saturation attack

I am having trouble here performing this attack on a block cipher. This is my block cipher, it is a toy with really bad diffusion just for the sake of performing a successful attack ...
1
vote
1answer
156 views

Is it safe to encrypt random data using ECB mode?

If I have 48 random bytes, is it safe to encrypt them using ECB mode? Or is there still a good reason to use another mode like CTR, CBC, etc.? Context is this: I am creating something like a TLS ...
1
vote
2answers
124 views

Is computing roots moduli a composite $N$ a hard problem without knowing the factorization of $N$?

Suppose that we are given $\mathbb{Z}_{N}$ and an element $x^u \in \mathbb{Z}_{N}$ with $u \in (0,l]$ where $l$ is the bit-size of $N$. Is it difficult to recover $x$ by knowing $u$ without knowing ...
0
votes
1answer
94 views

What can cause similar MD5 hashes

I have a set of MD5 hashes with huge similarities in the second half of the hash, (made up) examples: ...
1
vote
1answer
67 views

Is only one shared secret generated by ECDH per key pair?

I'm confused about ECDH. Using their public keys and private keys, two entities can arrive on a shared secret. But from the equations I've seen, it looks like ONLY the numbers present in their key ...
0
votes
0answers
65 views

Is there any pattern in points on EC?

I read some where in crypto.stackexchange answer (related to EC-SRP protocol) that there is pattern in points on elliptic curves, i.e. if given some points containing mix of correct and wrong points ...
0
votes
1answer
42 views

PKCS#7 signed data structure in signed PDF document

Is it mandatory to include PKCS#7 data (OID 1.2.840.113549.1.7.1) octet string into the sequence of PKCS#7 signed data? I mean if you want to sign PDF, you are basically adding PKCS#7 container ...
2
votes
0answers
36 views

During electronic voting, how does one hide the choice from Voting device?

Assume the following: I want to cast a vote during an election through an electronic voting system. For our system we make the assumption that the device one uses to cast the vote is potentially ...
-1
votes
1answer
55 views

Openssl library problem

I'm using openssl library and I've a problem with RSA_private_encrypt() and RSA_public_decrypt(). I'm using a key size of 256 bit with no padding of the input message. I've noted that when my input ...
2
votes
1answer
71 views

Is there an existing authorative definition of the cryptographic term 'pepper'

I can attempt to define the term 'pepper' as: In cryptography, a pepper is a something that is added to another value (for example a password) prior to a the value being hashed using a ...
0
votes
0answers
23 views

Device intercommunication with commands

I want to create a smart house project, and in that i bought some simple RF modules. Those modules don't support crypto out of the box but i want to connect them to a device that i would program to ...
1
vote
0answers
38 views

RSA, proof of correct work, if p is not a prime number [duplicate]

Is there any proof of correct work of RSA algorithm, if p is not a prime number? For example: n = p*q, p = p1*p2, where p1 and p2 are primes. Edit: I found that it's called Multiprime RSA, but i ...
2
votes
1answer
91 views

Can Poly1305-AES be used with AES-256?

I'm reading through Bernstein's The Poly1305-AES message-authentication code. The MAC is predicated on 16-byte block ciphers like AES and produces 16-byte authentication tags. However, Bernstein does ...
0
votes
1answer
214 views

Cryptography system by combining a block cipher and a stream cipher

I have to come up with a design for a cryptography system by combining a block cipher and a stream cipher. I can't seem to come up with anything on my own. Can someone point me in the right direction ...
1
vote
2answers
125 views

Prove that if we redefine the key space, we can assume Gen chooses a key uniformly

I am working on problem 2.1 in Introduction to Modern Cryptography 2nd edition by Katz and Lindell. 2.1) Prove that by redefining the key space, we may assume that the key generation algorithm ...
2
votes
1answer
89 views

Stacked LFSR - why not used?

New to cryptographic, weak in math. I have designed a PRG which consist of 33 LFSR's, each 32 bits wide. I use one of the LFSR's as "selector", using the 5 LSB from this register to select one of ...
0
votes
0answers
11 views

Keystore and configuration file

It appears that Java Keystore is often used by web server using a configuration file, with the password opening the JKS written in it and also the password protecting the specific entry. How could ...
0
votes
1answer
67 views

Assemble RSA keys from components

I'm studying openpgp cryptography and struggling to understand some things. I can't use pgp tool for generating keys and ecryption, but have to write a simple app to generate keys, encrypt and decrypt ...
2
votes
1answer
102 views

Is this a valid scheme to authenticate through a 'human-readable' certificate?

Let's say Alice wants to talk securely to Bob over the internet, and Eve is not only eavesdropping, but has managed to get into a MITM position. In this scheme Alice and Bob exchange $n$ (example $n ...

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