5 votes
Accepted

How do certificates help?

I can understand that the signature helps ensure that the public key was not tampered with. The certificate contains a lot of other information, which is all signed by the signature. An X.509 ...
  • 87.1k
4 votes

Create a new signature from existing DSA signatures

As far as we know, no, it's not possible to generate a new valid DSA signature from existing ones (for given public key), even for an already signed (known) message (assuming secure choice of ...
  • 128k
3 votes

Why private key is not used in Camenisch-Lysyanskaya Signature generation?

As pointed in comment, while the private key is not used in the signature step in the citation, that's only because $v^e=a^m\,b^s\,c\pmod n$ is the verification equation, and gives no way to compute $...
  • 128k
3 votes
Accepted

Signature operation of RSASSA-PKCS1-v1_5 requires private key. Superficial limitation, or are public parameters mathematically incapable of it?

Signature schemes are designed so that being in possession of the private key is required to sign messages. The public key in isolation only allows to verify signatures. Compare this to public-key ...
  • 813
2 votes
Accepted

What is the effect of solving short integer solution problem in Dilithium or any other post quantum signature scheme?

The hardness of SIS (or more precisely, the hardness of the module version of SIS: MSIS) is the assumption used to demonstrated the Strong Unforgeability of Crystal Dilithium under Chosen Message ...
  • 14.4k
2 votes
Accepted

Zero knowledge validation to check if private element is in a set hidden on a central server

Sounds like a scheme where $\phi$-hiding would work well. A scheme for a single secret element Write a publicly-known hash-to-prime function that maps guesses to primes of around, say, 128-bits (e.g. ...
  • 14.4k
2 votes

How do certificates help?

You start with a root CA certificate, say from the certificate authority Let's Encrypt. The self-signature on the root CA certificate isn't important; what's important is the public key—you can use it ...
2 votes

What is a website's private signing key used to sign?

What does the website's (client) private verification key sign? When a standard browser connects to a website, that browser is the client, and typically has no public/private key pair. Thus there is ...
  • 128k
2 votes

Why can't RSA signatures be forged algebraically?

Solving $s'^e = h' \mod n$ for $s'$ means calculating the $e$th root of $h'$ in $\mathbb{Z}/n\mathbb{Z}$. There is no efficient generic method to do that. The holder of the private key solves this ...
1 vote

How does signing with FORS work in SPHINCS+?

If by redundant you mean not relevant to the signature being verified, then yes. If by redundant you mean unusable for other signatures, then no. All of the square values in the tree represent WOTS+ ...
  • 14.4k
1 vote

Defending MITM attacks during key exchange

However, since the public key are modified, they can ensure that they are having a secure channel by ensuring their (alicePubKey + bobPubKey), or simplier, hash(alicePubKey + bobPubKey), is same. ...
  • 1,844
1 vote

What do people use non-extractable WebCrypto keys for?

The best thing about non-extractable keys it that they are literally the only thing on the web which the web server cannot compromise. The web server can easily change up your Javascript code, to ...

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