Linked Questions

64
votes
7answers
42k views

Why can't you work backwards with public key to decrypt a message?

As the title suggests, I am curious to know why you can't work backwards using a message, public key and encrypted message to work out how to decrypt the message! I don't understand how a message can ...
71
votes
3answers
60k views

SSL Certificate framework 101: How does the browser actually verify the validity of a given server certificate?

(Sorry I know this is a complete noob question and at the risk of posting a somewhat duplicate topic. I have a basic understanding of public/private key, hashing, digital signature... I have been ...
44
votes
2answers
7k views

Digital Certificate deployment: using two certs for each user?

At a large enterprise environment I have come across a deployment approach for Digital Certificates where each user is issued two (2) key pairs: One for signing documents, emails, etc. that is ...
34
votes
4answers
33k views

Can I use a private key as a public key and vice versa?

I have code to encrypt data using a public key and decrypt it using a private key. This is useful when a client wants to send data to a server and know that only the server can decrypt it. But say I ...
9
votes
4answers
2k views

If the public key can't be used for decrypting something encrypted by the private key, then how do digital signatures work?

I'm learning asymmetric encryption in the use case of ssl/tls protocol. I can understand that the public key (like a padlock) can encrypt (lock) something and only the private key can decrypt (open)...
7
votes
3answers
1k views

How do I actually air gap my CA computer?

I remember reading about the necessity of air gapping the CA computer (never connecting it to any network whatsoever, no USB dongles etc). I am preparing for setting up a number of certificates (...
6
votes
2answers
2k views

Verify digital signature without key public key in signature

When receiving emails, I sometimes see the following: -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 I found an integer overflow in PHP, in the conversation of dates to "Julian Day Count" function. ...
1
vote
1answer
1k views

Is this algorithm really end to end encrypted and secure?

I'm creating an anonymous chat where one of the premises is that the conversations are end to end encrypted. I'm using firebase so all the comunication between the clients and the server is SSL ...
2
votes
1answer
1k views

What is the difference between a digital signature and whole message encryption?

I am newbie in information security I am trying to understand the difference between a digital signature and encryption of a message. Lets consider simple example of email message. I understand how ...
4
votes
1answer
1k views

How to verify a server key exchange packet

I have a problem between two ends of an SSL connection. The server sends ServerKeyExchange and the client says the server key exchange packet is not signed correctly, so I want to check the signature ...
1
vote
2answers
998 views

RSA Digital signatures vs “encryption with the private key”

I found this statement In RSA crypto, when you generate a key pair, it's completely arbitrary which one you choose to be the public key, and which is the private key. If you encrypt with one, you ...
6
votes
2answers
338 views

Data Integrity in PKCs

This is a simple question but one which greatly confuses me. When you have a PKC, the public key can be accessed by anyone. Therefore, doesn't this mean that anyone can encrypt data? My question is ...
4
votes
1answer
522 views

Can OpenSSL decrypt the encrypted signature in an Amazon Alexa request to a web service?

OpenSSL newbie here. We're using OpenSSL to parse and verify the certificate and signature that Amazon's Alexa sends to external web services, following their list of requirements in the instructions ...
7
votes
1answer
780 views

How do certificates work in terms of encryption, hashing, and signing?

I think I might understand this stuff, but I want to be sure I've got the details correct. There is a lot of information out there on the high-level implementation of certificates, as well as the ...
1
vote
2answers
477 views

What if the Local Windows Cert Store is Compromised?

The diagram below illustrates chaining digital certificates up to a publicly trusted Root Certificate: I have been researching how trusted root authorities (such as GlobalSign or Verisign) are used ...

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