Linked Questions

96
votes
5answers
35k views

Why should one not use the same asymmetric key for encryption as they do for signing?

In an answer to a question about RSA and PGP, PulpSpy noted this: It is possible to generate an RSA key pair using GPG (for both encryption and signing -- you should not use the same key for both). ...
70
votes
3answers
59k 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 ...
64
votes
3answers
22k views

What is a good general purpose GnuPG key setup?

Since most key types can be used for multiple purposes, namely certification, authentication, encryption and signatures, one could simply use one key for everything - which is a bad idea, as ...
12
votes
2answers
3k views

Trying to understand RSA and it's terminology?

I get the gist of RSA but I'm mostly self taught so sometimes the phrases I picked to describe something don't match up with the widely accepted terminology. I'm trying to remedy this. I'm working ...
7
votes
3answers
4k views

Digital Signature and Verification?

AFAIK , When Alice wants to write a message to Bob -- she uses Bob's public key and encrypt the message - and then Bob - using his private key - use to decrypt it. So public key is used to decrypt ...
2
votes
1answer
8k views

Authenticated Diffie Hellman Key Exchange

It appears that the textbook version of Diffie-Hellman is susceptible to man in the middle attack and the use of digital signatures could prevent this attack from occurring. Digital signatures could ...
8
votes
1answer
4k views

Why do X.509 certificates have “Key Usage” attribute?

I can find their values and all details in the RFC, but I cannot find why it was decided to have this attribute in certificates, instead of leaving them to be multipurposes. Is there a reasoning ...
6
votes
2answers
1k views

Why can I sign but not encrypt?

-edit- After following a chain of links from this question I see this is similar/duplicate of Why should one not use the same asymmetric key for encryption as they do for signing? but this question ...
1
vote
3answers
7k views

What type of hashing method is used for the private key to encrypt for signing messages?

To use RSA for signing, Alice takes a hash of the message, encrypts the hash using her own private key, and appends the result (this is the signature) to the message. Eve can of course still decrypt ...
1
vote
1answer
3k views

How to encrypt with ECDSA?

Suppose there's a transaction in the blockchain in which a given address transfers bitcoins to whoever. I need to encrypt a message so only the owner of that address will read it. I have his public ...
2
votes
3answers
3k views

Public key Infrastructure

Here the MD5 hash is being encrypted with the private key of the sender. But I read in a paper that private key is only used for signing and not encrypting. Is the image wrong or can private key also ...
3
votes
1answer
1k views

Are DSA keys breakable?

Are the DSA keys breakable? If so, what is the maximum key size that is breakable with the latest technology ? Why are DSA keys not used during authentication? Can we use DSA keys for encryption?
2
votes
4answers
974 views

Can I use elliptic curve DSA in a secure message service?

I'm looking to design a system that allows a user of a crypto-coin such as Bitcoin to both have an online wallet and to be able to send and receive encrypted emails in the same system. The relevant ...
4
votes
2answers
906 views

Is it dangerous to use the same key (RSA) for both encryption (PGP) and authentication (SSH)?

Alice wants to send an encrypted message to Bob, but she also wants to connect to Carol's server. Are there any dangers associated with using the same RSA key for both PGP and SSH (other than a lack ...
0
votes
1answer
1k views

Encryption and Signature with same RSA private key

Talking about cipher-suites that use RSA both for sign of DH parameters and for digital signature. The keys used for these process are the same, or is there a public and private key for each one? If ...

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