Questions tagged [public-key]

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Does my receiver have a public key for email encryption?

I'm using an email service with encryption option and I need to send an encrypted email. So if I need my letter to be sent encrypted, I need to take my receiver's public encryption key and apply it to ...
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Best and safest way to store secret key used for PKA on server?

I interact with some API's that use PKA and I'm looking for the safest / best-practice way to store my secret key. The approaches I know are for example: Create a 0500 access directory on my server ...
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Standard for public-key authentication (separate from channel encryption)

Because of all the problems associated with "roll-your-own cryptography", I am looking for an existing standard for standalone authentication using asymmetric keys. Scenario/threat model ...
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Difference between trust anchors and certificate authorities

Trust anchors and (root) certificates authorities are often used interchangeably and it's easy to think that they are the same thing. The answer in Can an intermediate CA be trusted like a self-signed ...
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When using gpg2 to verify Qubes, the pub is different

I'm trying to verify the fingerprint of the Qubes Master signing Key (QMSK) however, I've run into some inconsistent output. For example: Qubes Os website & web of trust shows after executing the ...
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decryption of message using private key [duplicate]

I don't why we can decrypt the message using our private key if it's encrypted using our public key. If a message is encrypted using my public key, then how can I decrypt it using my private key? It ...
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Why is it not a good idea to simply encrypt the plaintext with the receiver’s public key? [duplicate]

What are some of the risks when encrypting "plaintext" with a receiver's public key? I have been Googling for hours, and been reading in the Computer Security Principles and Practice 3rd ...
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2 votes
2 answers
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How can I verify the hash of the plain text without being able to decrypt the cipher text?

I am building an E2EE chat app where there is one asymmetric key pair per group. Each user also has one asymmetric key pair. All messages in a group chat are encrypted with the group public key and ...
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What are possible implications of ignoring the ssh host key warning?

With password authentication you're basically giving your password to the attacker. At least that is my understanding. What about public key authentication? I hear that a private key never leaves your ...
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How can I prove the content of a PGP-encrypted message to a third party?

Imagine this scenario A StackExchange user sends you a PGP-encrypted message You decrypt the message and discover that you are being blackmailed You report the message to the admins but they are ...
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Getting Smaller Output From Public Key Cryptography In PHP

I have a website in a shared hosting environment, and I'm also planning to back up in multiple locations. All of that introduces vulnerability where the data could get intercepted, stolen, or misused ...
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Ways to encrypt data that will be available to specific clients [closed]

I want to store information on the blockchain, but some part of it is private and must be available to selected clients (for example, users who belong to a common company) How can this be done? The ...
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How vulnerable is security if a public key is swapped by active attacker if a key check is done?

Trying to understand this from a high level conceptually. It is obvious from all information on Asymmetric encryption that a public key can be of course, public and there isn't a danger of ...
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Why does Lightsail require the server's private key to connect via SFTP?

I am still learning about SSH, SFTP and private/public keys. My elementary understanding of keys is that the private key should remain on the machine it was generated on and never be shared. I have a ...
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-1 votes
2 answers
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Using Private Key for encryption

I want to implement simple software protection mechanism. This is how it would look like: My question is - is there any problem for me using the private key for encryption and public for decryption (...
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How does the inclusion of a subprime q value affect the Diffie Hellman equation for key exchange? [duplicate]

This is a follow on from this question: "Diffie-Hellman Key Exchange" in plain English In the answer to that question, the standard Diffie Hellman key exchange equation is derived: (g^a mod ...
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3 answers
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Not understanding why I should use public/private key encryption over password?

My knowledge about these topics is very elementary, please "school me" if I said something completely wrong, it would surely help me understand these things better. Now, to my issue. Now ...
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1 answer
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Enlighten Me Please Regarding PGP Encryption [duplicate]

I have somebody's public PGP key imported on my laptop (Debian Linux), but not their private key. When I encrypt a file to them using their public key, I can then decrypt it again even though I don't ...
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Using Public Key Cryptography for improving 2FA?

When using 2-factor-authentication using plain TOTP, the secret is stored on both the client and the server. This in turn means, that anyone with access to the database (and a key for it) knows the ...
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converting just a public key from PEM to DER using openssl

There are plenty of instructions for converting PEM certificates to DER which also pop up when looking for ways to convert public keys. These are among the options offered: openssl x509 -in cert.pem -...
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2 answers
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Deriving digital signature key pair deterministically from an arbitrary secret

Is there a scheme that let people derive public/private key pair from arbitrary secrets? As you may know, digital signature schemes have versatile use cases. The problem is, the key pair handling is ...
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1 vote
1 answer
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How securely should one treat their primary public key?

First of all, is my understanding correct that primary keys and subkeys are all key pairs consisting of a private and a public key? I get the rationale behind using primary keys and subkeys1, and why ...
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VPS host shows plain text "root" account password upon reinstall of unmanaged VM

I recently started using a VPS hosting service, that offers unmanaged VPS. It allows me to reinstall the VM at any point in time, choosing from a number of OS ISO files (doesn't have to be the same OS ...
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1 vote
3 answers
365 views

ssh and anonymity?

According to the man page, ssh by default sends multiple public keys from files in the ~/.ssh folder, one by one, until authentication success. Does that mean that the server side could know multiple (...
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Host Keys in Public/Private Key Auth

I've chased my tail into a late night circle thinking about public key authentication to cloud instances. As such, I have some questions on the function of host keys when authenticating an SSH session....
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Best ways to store private keys on a client?

I am currently writing a program that sends an encrypted file to the client, and I don't want the user to be able to access the file directly (though the client program will operate on it). Since the ...
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0 votes
1 answer
351 views

Verify signature without digest

I'm trying to verify that a smartcard (possibly doctored by an attacker) has access to the (ECDSA P-384) private key for which I was given a (signed) public key, in order to verify that the card is ...
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9 votes
3 answers
3k views

What happens when I encrypt something with my RSA Public Key?

I know encrypting something with my private key is used for signing. To prove that the message is indeed coming from me. But what about if I sign something with my public key? That would mean that ...
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1 answer
143 views

How public key is exported from a JWT

On this https://jwt.io/ application, you can paste a jwt and it returns you a public key. How is this public key generated, and how is it exported? Is it contained inside the JWT, and if it is, then ...
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