# All Questions

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### Decrypting the Encrypted hex applcation data with encryption keys [closed]

I am having all the keys, ...
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### RSA decryption from ciphertext using private key [closed]

I am sniffing a client side application traffic and I found some encrypted data. I am not able to decrypt it. Information which I have is Public Key: ...
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### What is the fastest elliptic curve operation f(P) in affine coordinates such that f^n(P)=P only if n is large?

I'm working with the affine representations of points of a Koblitz curve. I've read many papers that show that computing some functions, like $f(P)=3P$ can be computed faster than the standard way. ...
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### Polynomial multiplication and division in 2^128

I want to multiply and divide polynomials, and implement the extended Euclidean algorithm for polynomial greatest common divisors, over a Galois Field of size $2^{128}$. Moreover, I want to use the ...
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### How does OAEP improve the security of RSA?

The heart of OAEP algorithm used for RSA encryption are the cryptographic hash functions $H$ and $G$. Does everybody (so also an adversary) know these functions? If YES: How does it help the ...
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### Is this a sensible cryptographic protocol intending to reduce the impact of compromised security?

I'm in the process of designing a cryptographic protocol which will reduce the impact an attacker will have if they gained root access to a server storing data. The basic crux of it is that keys ...
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### Generate fixed length cipher text from arbitrary length plaintext

Using an encryption algorithm like AES, is it possible to generate a fixed length cipher text no matter how long the plain text becomes?
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### Hill-cipher, disordered alphabet

I am going to apply a simple substitution cipher to my input, then encrypt the result with a Hill cipher. How can this be broken, in a chosen-plaintext threat model? In other words, instead of the ...
117 views

### Help me describe/identify this challenge-response protocol/algorithm?

My area of expertise is reverse engineering, specifically embedded systems. I do attack cryptographic systems, but this largely involves key recovery or exploiting the implementation. I was asked to ...
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### Is Functional Encryption about Access Control over encrypted data alone?

Informally, In functional encryption system , a decryption key allows a user to learn a function of the encrypted data. But all i see is that the function acts as an access control over the data. ...
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### pseudo random sequence and permutation functions [closed]

Iam doing my Master thesis in enhancing of an encryption algorithm by using of a pseudo random sequence generators to create a 16*16 shared table and apply a permutation function on it. one of the ...
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### calculating beta for elgamal elliptic curves [duplicate]

Suppose we use elgamal elliptic curves for secure communication. Bob selects a prime $p$, an elliptic curve $E$, a point $\alpha$ on $E \pmod p$, and a secret integer $f$. Suppose that Bob has ...
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### SHA-1:Is there any mathematical result that gives us the minimum number of 1's in a 160-bit SHA-1 hash output?

Is there any mathematical result that gives us the minimum number of 1's in a 160-bit SHA-1 hash output? What is the probability that a 160-bit SHA-1 hash output contains at least 128 1's?
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### SHA-1: Is there any mathematical result that gives us the minimum number of 1's in a 160-bit SHA-1 hash output? [duplicate]

Is there any mathematical result that gives us the minimum number of 1's in a 160-bit SHA-1 hash output? What is the probability that the 160 bit result contains at least 128 1's?
38 views

### How to decipher this morse-like code message? [closed]

I found this little string that looks like Morse Code, but instead of dots (dits) has hearts symbols, I tried to change the hearts for dots, but I was not able to get any redable text. ...
101 views

### True random numbers generated by sensors

Is using sensor raw data a good way of generating true random numbers? I mean using an IPhone's gyro/accelerometer raw output as a base for generating an array of true random numbers.
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### Generating IV in TLS 1.2

I'm writing a TLS 1.2 implementation (in C#) using a custom protocol. My question is how to generate the IV attached to each message, I don't want to use RandonNumberGenerator because I've heard it ...
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### PKCS#11: Which CKK_types are supported by CKM_PKCS5_PBKD2?

On Solaris there's a function pkcs11_PasswdToKey() which is a wrapper of C_GenerateKey(). I made a simple test and it turned out ...
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### What is a fair exchange scheme?

The Wikipedia entry Fair exchange has only two lines, and the only paper I can find describing such a protocol is extremely complicated. Is this a new field in cryptology or can someone give an ...
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We're building a data service that is expected to go out through a single "fat pipe" channel. The design requirement says that the data in the channel must be protected by authentication and ...
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### Using an MD5 hash as a password

Suppose Alice is using a password prompt that only accepts up to 32 characters for any particular password. Memorization of long strings of random characters is not one of Alice's strengths, so she ...
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### CSPRNG in JavaScript using Audio and Video

I ported GnuPG to Javascript using Emscripten (not released yet). Now I need a good replacement for /dev/random//dev/urandom. ...
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### Why is the discrete log problem easy when the exponent comes from a binomial distribution?

I read in http://epubs.surrey.ac.uk/7219/2/esorics06.pdf that in exponential El Gamal the discrete log problem for recovering $m$ from $g^m$ can be made tractable when $m$ is drawn from a binomial ...
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### Why is the following RSA PRNG cryptographically secure?

One requirement states that the generator has to withstand the next-bit test. Consider the following PRNG, where we calculate next output $x_i$ via the formula $x_i = x_{i-1}^ e\mod n$. I can see ...
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### Is there a way to do fair exchange between two parties who don't trust each other?

Let's suppose we have an Alice who knows a secret key A, and Bob who knows key B. Using their own keys, they each encrypt a message (Alice encrypts $m_A$, Bob encrypts $m_B$) with their own key, and ...
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### Designing a security system from scratch with a custom protocol, suggestions needed

For the reasons I cannot go into details, I need to design my own protocol and overall security system which will be used to establish secure data exchange between various devices (most notably ...
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### Can someone help with the following hashes? [closed]

Here are a couple of hashes. I feel it should be easy (simple base conversions?) to decode them but I haven't succeeded so far. Can someone help? ...
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### Crypting text cheating wife on iphone [closed]

Wife received text looks like Chinese with boxes I am new to cheating with adware and crypting And embedding can I buy a service or app and cut and paste or copy these texts and they are Sent back ...
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### Combining LFSRs for Stream Ciphers: Why do we need high non-linearity?

Linear Feedback Shift Registers (LFSRs) can be excellent (efficient, fast, and with good statistial properties) pseudo-random generators. Many stream ciphers are based on LFSRs and one of the possible ...