Questions tagged [public-key]

An asymmetric cipher is an encryption scheme using a pair of keys, one to encrypt and a second to decrypt a message. This way the encrypting key need not be kept secret to ensure a private communication. Similarly in public key authentication, the verification key can be public and the signing key private.

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ECC public key encryption without symmetric cipher

Imagine the following scenario. A process is running in background and permanently encrypting some data. An adversary has full control of the process, e.g. it can dump the process memory any time and ...
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Is Googles Envelope Encryption the same as Hybrid Encryption?

Google is advertising the use of Envelope Encryption in their products with their KMS. By the description, it sounds very much like Hybrid Encryption. But since I could not find any reference to ...
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Is it possible to encrypt something using literally only a public key?

Most basic explanations of asymmetric encryption proceed as follows: Bob wants to send encrypted message to Alice. Bob and Alice each generate public/private key pairs. Bob gets Alice's public key ...
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ValueError: Unable to compute factors p and q from exponent d [migrated]

I created a script that helps me decrypt RSA key but apparently it doesn't work for all public RSA certificates. Here is the code: ...
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How is Diffle Hellman with RSA immune to man in the middle?

Alice and Bob want to exchange keys, Alice sends his half (the public key of the ephemeral key pair) signed with his private key and makes the public key available. Eve is bridging the connection so ...
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How is a public key able to verify a signature from the corresponding private key?

I understand how public/private keys can be used to 1- sign data of some sort with a private key, resulting in a signed document. 2 - Verify using the corresponding public key that the signed ...
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Requirements for RSA key parameters

Recently I'm working with a chinese vendor for POS devices and their devices use 2048bit RSA keys for signing binaries. I had to generate a public/private pair (so I can sign my own binaries) and I ...
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Is the role of public key/private key determined arbitrarily or mathematically?

I have read about conflicting information about the roles of public/private keys. In one article(Asymmetrical-key algorithms), it says: Simply put each party, say Alice, picks a private random ...
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Efficient receiver determination of public posted cipher

Assume there is a global message board, that people use to send messages to other people. Of course no one else but the receiver should know the content of the message, so senders use asymmetric ...
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Who verifies the trust of certificate authorities?

Background I am a novice in the field of cryptography and cyber-security, and while studying asymmetric-key encryption, I learned about the potential of a man-in-the-middle attack. To mitigate this ...
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Public Key generation for Ed25519 vs X25519

It is my understanding that EdDSA uses a slight variant of Curve25519 (typically used for ECDH), called Ed25519. Given the same private key, are the differences between the two algorithms enough to ...
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Symmetric key crypto secure communication infrastructure

Imagine that public-key crypto stops working. Are there any academic proposals out there that would explain how we could implement commercially viable secure communication based on the current ...
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Is there asymmetric encryption in SSH?

I've read in DigitalOcean article about SSH that in order for a server to authenticate a client: The server sends the client this encrypted message. If the client actually has the associated ...
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Understanding Montgomery's parameterization of elliptic curves

I'm having a bit of trouble understanding the translation of affine coordinates to projective coordinates in Montgomery curve ECM. Would be very thankful if someone could explain it by expanding the ...
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How can a public-key encryption scheme be used to construct a commitment scheme in the CRS model?

For a PKE scheme $(Gen, Enc, Dec)$, the most 'obvious' idea is to commit to an encryption of a bit and in the reveal phase maybe send $r_g$, $r_e$ where $r_g$ is the randomness of $Gen$ and $r_e$ is ...
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Why RSA-KEM is more secure than Textbook-RSA?

I am studying RSA-KEM but I can not see why it should be as secure as padding RSA messages (e.g with RSA-OAEP) when exchanging a key between two parties (say A and B). It is easy to see that Textbook-...
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Safest method for encrypting a file on a local machine

I am looking for a safe method to encrypt a local file on my machine. Let's say I have a file containing my logins and passwords -- how can I make sure that the encryption is reasonably sufficient in ...
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Can we retrieve his private key using his public key in ECC?

A paper wallet is the name given to an obsolete and unsafe method of storing bitcoin which was popular between 2011 and 2016. It works by having a single private key and bitcoin address, being printed ...
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True asymmetric ciphers beside RSA

Is there any TRUE public key cipher beside RSA? Most people would answer Elgamal or ECC, but for what is my understanding (and I know cryptography only superficially), those are not true asymmetric ...
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Authenticated encryption using libsodium's crypto_box_curve25519xsalsa20poly1305

It seems that crypto_box_easy, generates a random nonce and appends it to the cipher text in libsodium. I understand using the same nonce with the same key can be ...
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Is it safe to re-use the same p and q to generate a new pair of keys in RSA if the old private key was compromised?

Say I selected two large primes p and q for RSA and computed my public key (e, n=pq) and my ...
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Where to store public key of an asymmetric cryptosystem?

I am developing an application that uses ECIES encryption and I am currently storing private keys in secure place on each peer and storing public keys in a shared database (accessible by all peers). ...
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Suppose I capture encrypted data that I want to decrypt. Could I use a server farm to decrypt?

For argument's sake, let's say that I'm a bad actor who produces malware. I've infected around 10,000 computers and smartphones with my malware, which runs in the background and can be used to make ...
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Why are in asymmetric cryptography as many keys as people involved needed?

The question: "10 friends wish to establish secure communications between themselves using asymmetric-key cryptography. How many keys need to be known by each user?" was posed by my teacher. He says ...
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Will CT (Certificate Transparency) override the use of CAA and/or DANE/TLSA records?

I'd want to know if some of these competing technologies has more chance to survive. It seems they are thought to solve a similar problem by different manners and I'd want to stick to the most ...
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Zero knowledge proof that ElGamal ciphertext encrypts the opening of Pedersen commitment

Given ElGamal ciphertext for a message $m$ with a random $r$ as $(c_1,c_2) \gets (g^r, g^my^r)$ for a public key $y$, and a Pedersen commitment $C \gets g^xh^r$, I have been able to create a proof ...
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RSA exercises example

I have doubts about this question Consider the following textbook RSA example. Let be p = 7, q = 11 and e = 3. Give a general algorithm for calculating d and run such algorithm with the above ...
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What is the current state of the Conjugacy Search Problem in Matrix and Permutation Groups?

It results that I have come with a mathematical approach to solve the CSP (Conjugacy Search Problem) where the platform group $G$ is either a permutation group or a Matrix Group. From my part I ...
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Why use symmetric encryption with Public Key?

A. From what I heard (and I am beginner at a security/cryptography), if you have a payload that is very large, asymmetric is a no-go. B. Also, if you do have secret symmetric (e.g. AES) keys, you ...
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Is it possible to execute elliptic curve encryption on small sensor-tags CC2650?

I am working on a project wherein ECC needs to be implemented on small devices, namely, CC2650 sensor-tags for authentication. The ECC implementation should be on Contiki OS. I have read some articles ...
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What's the proper way of fitting hash digest to encryption scheme?

I would like to know what is the proper way of fitting the hash digest to the prime in which the encryption scheme operates. regardless if the bits of the hash digest is larger or smaller than the ...
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Securely derive AES and ED25519 keys from a ED25519 seed

Go's ed25519 package exposes a function which allows creating a private key from a 32 byte seed. See: https://godoc.org/golang.org/x/crypto/ed25519#NewKeyFromSeed The reason I want to use this is ...
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How does this formula work $(aG + bG) = (a + b) G$ in ECDSA?

Please explain how does this formula $(aG + bG) = (a + b) G$ work in ECDSA? According to the source: $a$ and $b$ are different private keys Suppose $a = 3$ $b = 4$ then the public key is $Q = aG$...
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Is there another group structure that is suitable for RSA other than $U_{pq}$?

I know that calculating the cardinality of $U_{pq}$ is infeasible and therefore it is extremely hard to break a code using Lagrange's theorem. But later on my studies i realized main principle of RSA ...
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What happens when i sign a public key with its private key pair?

I am not a cryptologist, just a cryptography user, so not sure if this is safe. I want to sign a public key with its private key pair. Is it dangerous to share this signature result along with ...
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Transition to post-quantum cryptography

Classical asymmetric cryptography is commonly based on the Discrete Logarithm Problem and Integer Factorization, which are known to be solvable with a quantum computer if it has the ability to run ...
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Is it possible to construct dataset for only another party to consult?

Is it possible to construct a dataset made of some kind of probabilistic encrypted indexes such that anyone can update the information contained in the set but only the one with a secret key could be ...
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What are some examples of out of bound channels that work over the Internet in practice?

If I want to verify a public key (be it RSA, PGP, etc.) with another client over the Internet only, what are some viable out-of-bound channels for verification? Which channels have been used in ...
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RSA figuring out the recipient of a ciphertext

I have this question I am trying to figure out the answer about RSA. I'd be grateful if someone could actually help me understand how the procedure would work. I am new to cryptography and with all ...
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Hashing using asymmetric cryptography

Every now and then, we read that some hashing function has been weakened or broken, but we almost never hear this for asymmetric cryptosystems like RSA or ECC. That's because while asymmetric ...
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What happens after sharing the secret key in quantum cryptographic schemes to send the message bits?

As a person working on the physics perspective of quantum communication, I understand the process upto which the quantum key is shared securely. What happens after this process to send message bits? ...
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Resetting a shared private key

I have a scenario with a user that needs to operate on common data from multiple devices but the link to the server is often offline. Unfortunately in the environment, I trust anything not directly in ...
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Recursive RSA encryption

I have a ciphertext $C$ encrypted with public key $pub_C$, which contains ciphertext $B$ and $pub_B$, $$C= E_{pub_C}(B\mathbin\|pub_B)$$ Ciphertext $B$ is encrypted with $pub_B$ and contains $pub_A$ ...
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Zero-knowledge commitment verification

Assume everything takes place in a prime field. Given the following: $g$ - generator $s$ - secret $E(K, m)$ - a public-key encryption function using public key $K$ and plaintext $m$ The ...
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End to end encrypted web chat app with stored messages in database

I am working on a web app with an integrated chat. All chats can only occur between two users - not more, not less. I am very concerned with security, so I would like to encrypt all chat messages with ...
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Determine the RSA private key from public key

I was told that you can determine the private key of an RSA encryption with the public key. I thought the point of a public key was to avoid letting people find the private key, but anyway, they said ...
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Encryption scheme that requires fewer keys for decryption than for encryption

I want to attempt creating a decentralized dead man's switch, so I'm looking for an asymmetric encryption scheme, with the following properties (ideally), or something close to them: There is a group ...
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Combine signature with encryption

I have some embedded device for which I want to sign and encrypt firmware files. Firmware updates are generated by me and may be installed by the customer. The encryption is supposed to protect the ...
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Vulnerability of low value generated key

I have read here that Elgamal is resistant to brute-force attack, because the group to where the key is selected is very large. But since the key generation is random, (i assume)there is a chance that ...
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Homomorphic Public/Private Key Encryption Scheme for Floating Numbers

Is there any public/private homomorphic encryption scheme that directly works on floating numbers or vectors of floating numbers? In our application, we want to find out if $$v_1 \approx v_2, \qquad\...