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17 votes

Is there any way to (irrevocably) *transfer* a private key to another person?

In PKIs, this situation is usually accomplished by ensuring Alice doesn't actually know the private key. The key is generated and stored in a hardware security module (HSM), which performs operations, ...
user71659's user avatar
  • 298
13 votes
Accepted

Why do we need a digital signature?

First an important point of terminology: the real question should be phrased "Why not just sign the whole message with the private key of Bob, send it to Alice, and verify it with Bob's public key?". ...
fgrieu's user avatar
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13 votes
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Finding Private key in RSA with public key, cipher text and plain text

No, there is no known efficient method to find an RSA private key from public key, ciphertext and plaintext, including when no padding is used and $e=3$. The best known method is factoring the public ...
fgrieu's user avatar
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13 votes
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Is there any way to (irrevocably) *transfer* a private key to another person?

Sign a message revoking Alice's old public key and certifying Bob's newly generated key. Include a timestamp from some timestamping athority and related metadata in the message. There's no way for the ...
DannyNiu's user avatar
  • 9,399
12 votes
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Clarification on the TLS verification process

The article is wrong, but not there. It's the previous sentence that's incorrect. "The first process is to take the signature on the bottom of the certificate and decrypt it with the CA's public ...
SAI Peregrinus's user avatar
6 votes
Accepted

What happens when a root CA loses its private key?

What happens when such a device is lost (fire, electronic fault, stolen, etc)? Assuming the HSM is stolen: The CA will likely inform the police so they can hunt the thief down, then they will ...
SEJPM's user avatar
  • 46.1k
6 votes

In PKI, with a hash-encrypted message (first hashed, then encrypted), how is the plaintext ever retrieved?

Signature generation is not encryption with the private key. Still, the basic flow of what you describe is correct for signature generation. However, the verification step is where everything derails. ...
Maarten Bodewes's user avatar
6 votes
Accepted

Converting raw ECC private key into ASN.1 DER encoded key

ASN.1 is a way of defining structures for data, and DER is a binary encoding of those structures. But they aren't describing any structures by themselves. Saying that something needs to be ASN.1 / DER ...
Maarten Bodewes's user avatar
6 votes
Accepted

How does TLS 1.3 provide authentication without using the public key to verify that the server has a private key?

... the public key from the certificate was used to encrypt the data to create a symmetric encryption key, hence the authentication took place on the factor of knowing the private key, as it is needed ...
Steffen Ullrich's user avatar
5 votes

Finding Private key in RSA with public key, cipher text and plain text

In order to find private exponent D we need to calculate the factors of N. e.g Finding the factors of a 64bit ...
Panos Kalatzantonakis's user avatar
5 votes

Is HIMMO For Real?

Is HIMMO For Real? ... I've not been able to find any critiques of the approach. First up, let me quote the HIMMO website itself which described it as broken at the time you asked your question: ...
e-sushi's user avatar
  • 17.9k
5 votes

Can public key cryptography survive quantum computers?

Current commonly used public key cryptography systems are based on the hardness assumption of factorization and/or discrete lograrithm. Both these problems are solved efficiently using Shor's ...
Meir Maor's user avatar
  • 11.8k
5 votes
Accepted

Who issued the first SSL certificate?

Spelunking through https://crt.sh, one finds a CA certificate for RSA Data Security, Inc., from 1994, but the oldest certificate it has issued has a validity period starting only on 1998-02-13. That ...
Squeamish Ossifrage's user avatar
5 votes
Accepted

MPC protocols in plain/CRS/PKI models

I understand that the CRS model refers to a setting where a common reference string is provided to all parties. How can this help in computation? (any pointer to a concrete protocol that uses such ...
Mikero's user avatar
  • 13.4k
5 votes

Is there any way to (irrevocably) *transfer* a private key to another person?

If an administrative message is identified just by being signed with a specific private key, you can't prevent any entity having a copy of that key from creating valid administrative messages. If the ...
Michael Karcher's user avatar
4 votes
Accepted

How are public keys securely and reliably obtained across the internet?

In a public-key infrastructure, there are two ways a public key can be trusted: either because it's signed by a certificate authority that you trust, or because you already have it in a list of ...
Gilles 'SO- stop being evil''s user avatar
4 votes
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How does registration authority verify entity's identity for SSL?

The answer these days is the Ten Blessed Methods Public CAs for the Web PKI (the PKI of the Internet's SSL/TLS services) are trusted by various entities, but by far the most important are the Web ...
tialaramex's user avatar
4 votes
Accepted

Can public key cryptography survive quantum computers?

Can public key cryptography survive quantum computers? Yes. All current PKC implementations might sooner or later be insecure due to sufficiently powerful quantum computer running Shor's algorithm. ...
AleksanderCH's user avatar
  • 6,462
4 votes

Blockchain use in record management

The purpose of the bitcoin block chain is to provide an imitable public ledger. If you read the original bitcoin paper you will see that the block chain is but one component of a larger whole that ...
dave.zap's user avatar
  • 493
4 votes
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TLS encryption with a self-signed PKI and Python’s asyncio module

Since I stumbled on this checking something else, a few minor points A CA doesn't sign a CSR; it signs (issues) a cert that has some important data taken from the CSR but much data different. The ...
dave_thompson_085's user avatar
4 votes

What's the downside of using X.509 in SSH instead of PKI

OpenSSH supports certificate authentication -- it has for about a decade -- but doesn't use X.509. It uses a custom (simpler) certificate format. My understanding is that this choice was made for non-...
mmalone's user avatar
  • 141
4 votes

How to securely share AES key between two remote devices (client and server) through UDP protocol?

You don't transfer the key, not at least un-encrypted. There are several ways to "establish a shared key" between authenticated systems. Using key exchange schemes such as Diffie-Hellman, ...
DannyNiu's user avatar
  • 9,399
4 votes
Accepted

What exactly is Let's encrypts chain.pem file?

When requesting a certificate one sends a Certificate Signing Request, containing the information to be signed by a CA, to that CA. The CA responds with the resulting certificate and the chain of ...
SAI Peregrinus's user avatar
3 votes

How can I verify a client's identity by requesting a digital certificate?

Ok, I'll assume you have collected the data from the form. The next step is to confirm the user's identities based on the certificates they have. For this you have two options: Send a S/MIME signed ...
SEJPM's user avatar
  • 46.1k
3 votes
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How are certificate status obtained on browsers?

OCSP is not susceptible per se to MITM attacks, but it does have other problems: Most browsers used to soft-fail, e.g., if they couldn't get the OCSP response for some reason, it allowed the ...
Conrado's user avatar
  • 6,464
3 votes
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Understanding need for PKI

Your understanding is correct. PKI would be the service that verifies that Bob's public key really belongs to someone named "Bob". As long as Alice trusts the certificate authority that certified Bob'...
forest's user avatar
  • 15.3k
3 votes

Encrypt text message with Wireguard public key

Wireguard is not PGP. In particular, Wireguard doesn't do several things that PGP does, because doing those things is very difficult to do securely. One of those things is encrypting anything with a ...
SAI Peregrinus's user avatar
3 votes

What's the downside of using X.509 in SSH instead of PKI

The fundamental difference is in how (and wether) the clients and servers identity is validated. In X.509, keys are authenticated by virtue of being issued by a trusted certificate authority. That ...
Kevin Keane's user avatar
3 votes
Accepted

Why is factorial used in Pollard's $p - 1$ algorithm?

Fermat theorem Lies behind this second factorization scheme, known as pollard p-1 method. suppose odd composite integer n to be factored has prime divisor n, with the property that p-1 is a product ...
SSA's user avatar
  • 640

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