a transformation of information to make it unreadable to outside observers

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1answer
38 views

Encryption on a compressed file

Can I do encryption on a compressed file and again decompress the file after decryption to get the original data?
2
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2answers
441 views

What if p and q are not distinct in RSA Crypto System? What could go wrong?

In RSA Crypto System we choose p and q such that they are distinct primes. Calculate n=pq and phi=(p-1)(q-1). Then e is chosen for public key (n,e) s.t. gcd(e,phi)=1
0
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1answer
27 views

Issues in RSA setup

Suppose we have public key: $$n= 1015, e= 3$$ and private key: $$d= 635, p= 35, q= 29, \phi(n)= 952$$ For $m = 100$, we have $$c = m^e ~mod~n = 100^3 mod~1015 = 225.$$ To decipher this, let us ...
1
vote
1answer
46 views

How to revert a carryless polynomial multiplication?

In the carryless multiplication of two polynomials in a 8bit environment. Is it possible to obtain the original 8bit values from the result? As an example: (x11 + x10 + x9 ) + (x7 + x5 + x4 + x3 + ...
7
votes
2answers
58 views

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 ...
2
votes
1answer
45 views

RSA Encryption & Anonymity

Considering plain RSA encryption, assume we have B who wants to send 10 messages to either A1 or A2. The recipients' public key, namely the exponent e1, e2 and prime product n1, n2 for A1/A2 ...
1
vote
3answers
270 views

Formula for sufficiently lengthy encryption key?

As you add length to an encryption key, at some point the message becomes impossible to brute-force decrypt. This is because at that point, if you go through all the possible keys, you'll get many ...
0
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0answers
60 views

More about the ESP tree

In this previous question I had asked about the intuition behind looking at the ESP tree. One place where it is used is to construct an approximation of arbitrary distance functions $d : [m]^n ...
0
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1answer
77 views

RSA Decryption from Simple Public Key Values

I'm a little stuck trying to figure out how to decrypt some messages and could use some hints as to what I may be doing wrong. I was given a series of integer values that make up my cipher text. Here ...
4
votes
3answers
132 views

Data Compression: Which one is Better “Compress before Encrypt” or “Encrypt before Compression”

Which one is better approach do data compression before encrypting it or Encrypt data before compression ? I think it is biased towards the application requirement. Please share your views.
2
votes
1answer
890 views

One time pad, get plaintext using ciphers encoded with the same key

I'm trying to solve a problem: I have 11 ciphers encoded with the same key. My aim is to decode target cipher. If I do xor C1, C2 (ciphers encoded with the same key) I do get M1 xor M2 (where M1, M2 ...
6
votes
4answers
431 views

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 ...
7
votes
5answers
265 views

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 ...
8
votes
3answers
471 views

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? ...
10
votes
3answers
302 views

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 ...
9
votes
2answers
2k views

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 ...
10
votes
5answers
257 views

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 ...
69
votes
5answers
4k views

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. ...
13
votes
4answers
4k views

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 ...