Encryption is the process of transforming plaintext using a cipher into ciphertext to make it unreadable to anyone except those possessing the key. Decryption is the process of transforming that ciphertext back into plaintext, using the key.

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To prove $r \cdot f_1 +f_2 \cdot (s+1)$ is secure

We define the polynomials $r, f_1,f_2,s \in R[x]$. Where $r$ is a random degree 1 polynomial and $s$ is a random polynomial such that: $degree(s)=degree(f_1)=degree(f_2)$, let $R$ be $\mathbb{Z}_p$ ...
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45 views

how can I understand nonlinear coding for error detection

I want to understand how nonlinear coding can detect the errors in cryptography computing . actually I don't know what these code doing and what are the codewords in this system. now can any body ...
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33 views

vector space retrieval model

In tf-idf weighting scheme of vector space model, weight matrix is calculated as a product of term frequency(tf) and inverse domain frequency(idf). I need paillier dot product calculation here. Can ...
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4answers
284 views

Why are primes important for encryption

Why are primes so important? Why can't we just use a random number? My guess is that it's because finding a random prime require more computing power, than finding a random number. Can anybody confirm ...
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1answer
75 views

one time pad regarding

If I had two ciphertexts $$c_1 = m_1 \oplus y_1 \text{ and } c_2 = m_2 \oplus y_2$$ will it be possible to obtain $$z_1= (m_1 \lor m_2) \oplus y_1 \oplus y_2 \text{ and } z_2= (m_1 \land m_2) ...
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48 views

Perfect secrecy of a crypto system

Suppose we have the following crypto system: $P = C = K = \{0, 1, . . . , n − 1\}$, $E_k(x) = (x + k) \bmod n$ and $D_k(y) = (y − k) \bmod n$. Prove that the crytosystem has perfect secrecy. Perfect ...
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2answers
154 views

What would be the best plain text Cryptography method without the use of a computer? [on hold]

What would be the best Cryptography method without the use of a computer? This could be a list of the current options available, that could be used without the use of a computer ...
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1answer
90 views

Dancing confusion with Daniel J. Bernstein's stream ciphers

I know of Salsa20 which won the ESTREAM competition. This is dated of 25 Dec 2007. There is also the ChaCha20 stream cipher (cr.yp.to/chacha.html). This claims to increase the amount of diffusion ...
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0answers
86 views

How represent message in Menezes–Vanstone elliptic curve cryptography

I ask about represent message in Menezes–Vanstone elliptic curve cryptography I now encrypt function as follow $C_1 = (M_1 * K_1) mod\ P$ $C_2=(M2 * k_2) mod\ P$ My question is about how much the ...
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0answers
44 views

Encryption key input by a user [on hold]

I was looking for some research papers where the security scheme is using 'user input' key method (but could not find). I mean, some approaches where user will be the one who will put keys for ...
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3answers
676 views

Why does the recommended key size between symmetric and assymetric encryption differ greatly?

In various articles it is mentioned that for secure communications, the recommended key sizes are 128-bit key size for symmetric encryption (which makes it $2^{128}$ possible keys?) and 2048-bit key ...
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1answer
131 views

How to customize a standard encryption algorithm?

I want to modify and customize AES encryption algorithm and develop a variant of it. What factors should I consider so that it does not become weaker? What skill sets would be required to undertake ...
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0answers
31 views

electronic voting system [migrated]

Was looking at cryptocurrency and how, as a non techy, to get involved when I began thinking about the security of it being developed to undermine the stranglehold bankers have on economy and the ...
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0answers
46 views

Security considerations on using key derivation to create one-time keys for block ciphers

I'm planning to do some block encryption with AES and Blowfish (both with 256 Bit keys) chained. Master key generation: A 32 byte long persistent (over many years) master key is derived from a ...
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0answers
60 views

How many bits should my random number be if I used 2048 bits to create my RSA key [closed]

I am using pyCrypto's RSA module/library and have created an public/private key using 2048 random bits from a hwrng. I then want a person/computer who has the public key to generate a random bit ...
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0answers
74 views

Interactive assumptions not falsifiable?

Can someone explain why an interactive assumption is not falsifiable? Maybe I'm misunderstanding what the statement means, but isn't even a non-interactive assumption interactive, but just with a zero ...
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0answers
33 views

Active Sbox count in PRESENT Cipher [closed]

Can any one please tell me how to calculate active Sbox directly or is there any c code for it?
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1answer
119 views

rsa public and private keys

I have a question about RSA key generation. This is a simple RSA algorithm: Choose p = 3 and q = 11 Compute n = p * q = 3 * 11 = 33 Compute ?(n) = (p - 1) * (q - 1) = 2 * 10 = 20 Choose e such that ...
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0answers
48 views

Asymmetric encryptions' computational complexity [duplicate]

I need to know the computational complexity of the public key encryption (e.g. Paillier), please. (i.e.Paillier in his paper mentions that the computational complexity of most of public key ...
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1answer
32 views

FEAL-4 Fk Function 4 Rounds

As I understood in FEAL-4 it needs 4 pair of round keys. Which means that we need to launch Fk function 4 times, but the problem occures on the 2nd round. At first round we have original 64 bits key ...
117
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7answers
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Should we MAC-then-encrypt or encrypt-then-MAC?

Most of the time, when some data must be encrypted, it must also be protected with a MAC, because encryption protects only against passive attackers. There are some nifty encryption modes which ...
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1answer
115 views

Secure double encryption using CPA and CCA

Do you mind if you give me any hints, links or ideas about how to improve the security of double regular encryption and decryption, by using CPA game and CCA game, it sounds interesting question, and ...
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1answer
88 views

My own encryption algorithm - if someone can brake [closed]

I wrote recently my own encryption algorithm. I want to test it so, since I know that here are a lot of professionals, I will write here some encrypted text and if someone is able to decrypt it please ...
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1answer
46 views

Oblivious transfer variation question

Now I am doing a variation of the oblivious transfer, I have to use 2 people, pebbles, and boxes. I need to find out if who has a larger number between Alice and Bob (variation of Yao's Millionaires' ...
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1answer
102 views

how to calculate non linearity of AES S-box?

S-box has to satisfy different design criteria. How to calculate non-linearity , propagation criteria for an AES S-box?
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135 views

Can a secret message be securely transmitted within a MAC tag?

A sender wants to transmit an ultra secret code $M$ which could be either 'go', 'stop' or 'wait'. This could be any selection of code words really and adopted for any use such as transmitting short ...
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1answer
97 views

Reversing a Psuedo Crytographic Hash [closed]

I'm trying to get a better understanding of cryptographic hashing. Take the example transformation function below, is it possible to reverse this formula to solve/isolate for message[i]? ...
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1answer
37 views

Repeating something encrypted and non-encrypted?

If one wants to keep the receiver's name non encrypted, but it also appears in the encrypted message - will it leak information? (other than the receiver's name, of course.) Let's assume a "bad" case ...
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30 views

how can I change representation of point to Jacobian coordinates in Edward's Curve

I want to simulate this algorithm but I want to change it's output to Jacobian coordinates. what should I do ? In the other way how can we change extended homogeneous coordinates to Jacobian ...
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0answers
21 views

How to compare security parameters of different schemes (Sign-Encrypt, Encrypt-Sign, etc)? [duplicate]

How can one compare the security parameters (confidentiality, integrity, non repudiation, etc.) for different schemes (Sign-Encrypt, Encrypt-Sign, Sign-Encrypt-Sign, Encrypt-Sign-Encrypt)? Are there ...
0
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0answers
26 views

Encrypt algorithm [duplicate]

Is it possible to encrypt an algorithm? What I mean by this is have a remote/cloud computer execute a program that will process some data... And the remote computer would not be able to know anything ...
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1answer
133 views

Why there are limitations on using encryption with keys beyond certain length?

I am writing a java program to encrypt a message using 256-bit AES encryption, but I am getting illegal key size error, I have read that I have to use some JCE ...
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2answers
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Encryption algorithm designed to be easy to decrypt by machine but impractical to decrypt by hand

I am looking for - or considering the design of a new - encryption algorithm that does not use variable keys, such that it is easy for a computer to encrypt and decrypt any message regardless of its ...
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39 views

Encryption using elliptic curves

What is currently the best way to actually encrypt a message using elliptic curves? I'm looking for an algorithm like ElGamal, but more efficient, since ElGamal outputs a tuple of two points for every ...
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46 views

RSA OAEP: prevention of partial decryption of ciphertexts

I'm trying to understand RSA encryption (as a beginner in cryptography). go on this wiki page http://en.wikipedia.org/wiki/Optimal_asymmetric_encryption_padding scroll down to the 2 numbered points: ...
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How secure is AES-256?

The cipher AES-256 is used among other places in TSL/SSL across the Internet. It's considered among the top ciphers. In theory it's not crackable since the combinations of keys are massive. Although ...
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59 views

Bilinear Map vs Inner Product [migrated]

What is the difference between a Bilinear Map and a Inner Product?
2
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1answer
66 views

what are multi-primes and how are they different from semiprimes?

I came to know of semiprimes recently. The simplest explanation of semiprimes is you take any two prime numbers and you multiply them, say 3*11 = 33 in which case 33 would be a semiprime. The numbers ...
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33 views

Real life RSA/El Gamal examples

Can someone direct me to examples of El Gamal and RSA that would be similar to real life (i.e. large primes). I wrote a code for encryption and decryption, but I wanted to test it against some larger ...
3
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2answers
329 views

Is it possible to match encrypted documents using user-defined search terms?

Suppose I am storing a number of encrypted documents in a database. I would like to make it possible to identify the subset of documents whose contents match user-specified search terms without a) ...
2
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2answers
91 views

Large file validation on an embedded system through hash and encryption

As a preface, I have to say that I am a noob in this area. Having said that, I will ask the question. I have a situation where I need to validate and protect against tampering a handful of large ...
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0answers
44 views

Mifare Classic and crypto1 algorithm

Mifare's Crypto1 algorithm uses a 48-bit LFSR. What does the 48-bit LFSR do exactly ?
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76 views

For calculating the index of coincidence for each sequence

I was learning about the finding the key length reading the following web site... http://practicalcryptography.com/cryptanalysis/stochastic-searching/cryptanalysis-vigenere-cipher/ and I really don't ...
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1answer
58 views

What Java actually stores inside Keystore when generating Keys?

When we use Keytool to generate a Keystore to store Private/Public keys, what Java actually stores inside the Keystore file ? I ...
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59 views

Modes of encryption for hard drives?

What are the currently recommended modes of encryption for large disks? Basic requirements would seem to be that you can update an encrypted sector independently of others, which rules out most ...
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1answer
112 views

Where have all the cypherpunks gone?

In 1992, cypherpunks was created as a mailing list for activists advocating for cryptography. Arguably, the cypherpunks mailing list was the foundation for the movement and the centre of it all. ...
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40 views

How many characters per block in an El Gamal ECC cryptosystem?

While I look for how many characters that can be encrypted using the The elliptic curve ElGamal cryptosystem. of each block found for these lines. But I can not understand Actually in our case we ...
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How can I start the following crypto project?

(Cryptography: encrypting files before storage in the cloud): The project consists of a software implementation of a method to pre-process a file before storing it on a cloud storage server so that ...
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1answer
34 views

plaintext distribution ,perfect secrecy cryptosystem

I have been trying to solve the next problem: let pi be a perfect secrecy cryptosystem with specific plaintext probability distribution. How to prove pi will have perfect secrecy for all other ...