An asymmetric cipher is an encryption scheme using a pair of keys, one to encrypt and a second to decrypt a message. A special class of asymmetric ciphers are public-key ciphers, in which the encrypting key need not be kept secret to ensure a private communication.

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How can I prevent a message replay with RSA?

I am using RSA to encrypt some data but I would like to eliminate the possibility of message replay. By message replay I mean sending a valid message multiple times to the original recipient. It is ...
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A set of key pairs and one hash to secure them

I have a simple problem: I have a set of users' ECDSA key pairs, and say I want to encrypt them with a simple algorithm. I have access to one variable that uniquely identifies the user, so I hash it ...
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In RSA, do I calculate d from e or e from d?

In the original paper introducing RSA, it is implied that one should first choose $d$ and then calulate $e$ from $p$, $q$, and $d$. However, I have found in other places (such as the wikipedia article ...
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Can a computationally unbounded adversary break any public-key encryption scheme?

Assume there is a public-key encryption scheme $(KeyGen, Enc, Dec)$ with perfect correctness (i.e., for all messages M and valid key-pairs (PK,SK), we have $Dec_{SK}(Enc_{PK}(M))=M$). Will there ...
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How should one implement a delegated shared trust protocol?

Consider the following (probably naive) scenario. Alice, who is very limited in her knowledge of security in general (clueless about securing a private key for example), wishes to delegate certain ...
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What is Identity-Based Encryption (IBE) and why is it “better”?

Most CS/Math undergrads run into the well-known RSA cryptosystem at some point. But about 10 years ago Boneh and Franklin introduced a practical Identity-Based Encryption system (IBE) that has ...
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Basic explanation of Elliptic Curve Cryptography?

I have been studying Elliptic Curve Cryptography as part of a course based on the book Cryptography and Network Security. The text for provides an excellent theoretical definition of the algorithm but ...
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646 views

Digital Signature Algorithm signature creation

I was studying DSS from "Cryptography and Network Security" by William Stallings. What puzzled me was the DSS approach figure described in the text. It says it uses Public and Private Keys for ...
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Does NTRU decrypt correctly now?

The NTRU public-key cryptosystem has a lot of interesting properties (being resistant to quantum computer attacks, being standardized by several important bodies), but it also has a pretty unique ...
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Why is public-key encryption so much less efficient than secret-key encryption?

I'm currently reading Cryptography Engineering. After giving a high level explanation of the difference between secret-key encryption and public-key encryption, the book says: So why do we bother ...
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Types of Cryptography for a 4-8 bit microcontroller

This is more of a research question. I was wondering what types of crypto algorithms would work best on a small 4-8 bit micro controller. I recently read a paper called Security Considerations for ...
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Is public-key cryptography the only option in this scenario?

Two parties: a client and a server are to a agree on a symmetric key. Both the client and the server are aware of a master password. The way this is currently done ...
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Is there an algorithm to find the number of intersections of two sets?

Suppose both I and my friend have a set of integer numbers. We want to know the number of common elements in our two sets but without knowing elements of the sets of each other. So I don't want my ...
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Applications of Group Ciphers

I've been reading a paper [1], and I've ran across something called a "Group Cipher", which is similar to homomorphic encryption, with an important difference. In homomorphic encryption we have an ...
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2answers
485 views

How exactly are GPG keys mathematically related, and prime numbers inside of GPG general

Before anyone suggest it, I've yet to pick up "Applied Cryptography" I'm planning on picking it up the next time I visit amazon. I know that the keys are somehow mathematically related, and I know ...
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6answers
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How does asymmetric encryption work?

I've always been interested in encryption but I have never found a good explanation (beginners explanation) of how encryption with public key and decryption with private key works. How does it ...
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Are any of the major asymmetric ciphers distinguishable (EG, RSA, ECC)?

Related to "Is it possible to derive the encryption method from encrypted text?". Given ciphertexts generated by any of the major asymmetric ciphers (RSA, ElGamal, ECC, etc..) can these ciphertexts ...
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Are there asymmetric cryptographic algorithms that are not based on integer factorization and discrete logarithm?

In the computer security class (in which cryptography is a big chapter) that I took, I remembered the professor said about current asymmetric cryptography algorithms are based on integer factorization ...
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Is it possible to create an asymmetric cryptosystem where the private keys are not easily verifiable as such?

Plaintext that consists of an RSA key is easily recognizable as such, because it satisfies certain mathematical properties, in particular (See the answer for Why can an encrypted private key be brute ...
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Is key size the only barrier to the adoption of the McEliece cryptosystem, or is it considered broken/potentially vulnerable?

A recent paper showed that the McEliece cryptosystem is not, unlike RSA and other cryptosystems, weakened as drastically by quantum computing because strong Fourier sampling cannot solve the hidden ...
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RSA with small exponents?

Just to establish notation with respect to the RSA protocol, let $n = pq$ be the product of two large primes and let $e$ and $d$ be the public and private exponents, respectively ($e$ is the inverse ...
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2answers
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Protocol to generate Client Certificates at the start of a SSL session automatically?

A more secure form of 'cookie' could be created for SSL communications through the following method. The client generates and requests the server to sign a certificate. Then the client authenticates ...
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How can SSL secure a two-way communication with only one key-pair?

As I understand it, SSL involved the use of a public-private key pair. How does this enable two-way communication? Suppose I have some server with which I wish to communicate securely. I connect to ...
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How can I use asymmetric encryption, such as RSA, to encrypt an arbitrary length of plaintext?

RSA is not designed to be used on long blocks of plaintext like a block cipher, but I need to use it to send a large message. How can I do this?