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Questions tagged [encryption]

a transformation of information to make it unreadable to outside observers

Encryption is a mathematical transformation of data (the plaintext) into a ciphertext which is unreadable to principals who do not possess the proper key. Use this tag in addition to if your question is specifically about encryption or decryption.

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Why hasn't there been an encryption algorithm that is based on the known NP-Hard problems?

Most of today's encryption, such as the RSA, relies on the integer factorization, which is not believed to be a NP-hard problem, but it belongs to BQP, which makes it vulnerable to quantum computers. I wonder, why has there not been an encryption…
Ken Li
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Why is encrypting with the same one-time-pad not good?

To encrypt a message $m_1$ with a one-time-pad key $k$ you do $Enc(m_1,k) = m_1 \oplus k$. If you use the same $k$ to encrypt a different message $m_2$ you get $Enc(m_2,k) = m_2 \oplus k$, and if you perform Xor of the two ciphertext you get $$(…
Ran G.
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Is it possible to create a "Time Capsule" using encryption?

I want to create a digital time capsule which will remain unreadable for some period of time and then become readable. I do not want to rely on any outside service to, for instance, keep the key secret and then reveal it at the required time. Is…
Micah Beck
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If P=NP, are there cryptosystems that would require n^2 time to break?

If P does equal NP, will it still be possible do design a cryptosystem where the optimal cryptanalysis algorithm takes, say, the square of the time taken up by the legitimate encryption and decryption algorithms? Do any such algorithms already…
S.LAKSHMINARAYAN
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How does a wifi password encrypt data using WEP and WPA?

How does the password that we enter (to connect to a wireless network) encrypt the data on the wireless network? Through my reading I am not sure if the password that we enter is the same as the passphrase. If that is right then how can the…
MR.NASS
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How is the key in a private key encryption protocol exchanged?

Windows NT used a point-to-point protocol where a client can communicate "securely" with a server by using a stream cipher to encrypt an array of messages with some key $k$. The server also encrypts its response with the same key $k$. But how is it…
codd
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Why do public key systems involve private keys?

I read up the definition of a public key cryptosystem. It mentions there is a public key and a private key. That's confusing. Why is it called a "public key" system if it involves a private key as well?
rohit sharma
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Problem with the pseudo random number generator One-Time-Pad

I've started learning cryptography in class and we've come across One-Time-Pads, in which the key (uniformally agreed upon) is as long as the message itself. Then you turn the message into bits, do $XOR$ and get the cipher text. This encrypts the…
Ski Mask
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Running an algorithm on data remotely and ensuring answer has not been tampered with

I´ve been thinking about this particular computing/crypto/database problem for years and I just want to know if there are already solutions to it. To be honest I don´t even know what field this problem belongs to exactly. In a nutshell: person A has…
Robin A
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How can encryption involve randomness?

If an encryption algorithm is meant to convert a string to another string which can then be decrypted back to the original, how could this process involve any randomness? Surely it has to be deterministic, otherwise how could the decryption…
CJ7
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Key secrecy vs Algorithm secrecy

it's a well known statement that "Cryptographic security must rely on a secret key instead of a secret algorithm." I would like to ask about some details about it. And which are their differences? I see the obvious thing that for a multi user…
Hernan_eche
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After implementing a novel encryption algorithm, how would one go about analyzing its security or get help from others in doing so?

Preface: This question was originally asked on Theoretical Computer Science, and the kind people there referred me to this web site. It is being repeated here in an attempt to find a satisfying answer. Over the years, two novel encryption…
Noctis Skytower
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Can I prove that I have x such that f(x) < c without revealing x?

I'm interested in applications to verifiable computing. Let's say Alice would like to find an x such that f(x) < c for some real-valued function f and some c of Alice's choosing, so she hires Bob who has a powerful computer. Bob finds such an x, but…
Imran
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Is running AES NI in parallel possible (one encryption per core/thread)?

AES NI seems to perform AES operations much faster than doing in software. However, if I have a machine with a large number of cores (say 32 cores), can I perform 32 AES encryptions using AES NI instruction i.e. one per core? Or can I just run one…
kartik1507
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Perfect Probabilistic Encryption still requires key length about as long as message

Let $(E,D)$ be a probabilistic encryption scheme with $n$-length keys (given a key $k$, we denote the corresponding encryption function by $E_k$) and $n+10$-length messages. Then, show that there exist two messages $x_0, x_1 \in \{0,1\}^{n+10}$ and…
user108609
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