Questions tagged [certificates]

A certificate consists of a public key and information about the owner (e. g. the name of a person or server).

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4k views

Extra attributes in a certificate signing request

When creating a certificate signing request, there is a part where openssl says "Please enter the following extra attributes to be sent with your certificate request". One of these is a challenge ...
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485 views

Can (EC)DH keys be used as the signed content in X.509 certificates?

From Wikipedia's article on ECDH: The public keys are either static (and trusted, say via a certificate)… Also see this question on this very site. These indicate to me that a certificate (maybe ...
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How is the root certificate transmitted to pc?

i understand that the purpose of root certificates and CA's is to ensure that the communication parties are who they say they are. But how is the root certificate acquired? Is it not possible that ...
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1answer
139 views

X509 certificates: Two Algorithm Identifiers?

I'm wondering why there are two Algorithm Identifiers in a X509 certificate. One is in the "to be signed" part and the other one is at the end right before the actual signature. Are they used for the ...
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x509 Certificate Signature

I've got a question about the signature of a CA. As I understand, the CA takes the public key of the client and signs it with his own private key by using "md5WithRSAEncryption" (like explained here: ...
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Do people sign my subkey?

So, I've generated my GPG key pair. Created a subkey for signing and a subkey for encryption. Exported the whole thing, removed my master key pair to a secure place, re-imported only the subkeys. Now, ...
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638 views

Are any Certificate Authorities using 4096 bit keys for their intermediate and root certificates? [closed]

Are any Certificate Authorities using 4096 bit keys for their intermediate and root certificates? I know you can, of course, use a 4096 bit key for your server certificate, but I usually see 2048 bit ...
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45 views

Shortest Path for Certificate Network

I was reading an example from my textbook about verifying a certificate from a client using a certificate network. The example in the book is as follows: A issues a certificate to B. A issues ...
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X509 certificate

I am studying the X509 certificate structure and here is an OpenSSL configuration file for generating the certificate. ("sth" just mean the actual string is removed) ...
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Could someone reuse client certificates?

To my understanding, if a server “cert+key” (RSA) is compromised, than the SSL/TLS network traffic can be decrypted. What about a client “cert+key” (RSA)? Could someone reuse client certificates? ...
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189 views

Creating certificate: Where is my private key stored?

I have some problems to understand the storage of my private key when a CA generates my key pair. Let's assume the CA creates my key pair, issues the certificate with my public key and signs it with ...
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1answer
886 views

What happens when a root CA loses its private key?

Certificate Authorities normally keep their private keys inside dedicated Hardware Security Modules (HSMs). What happens when such a device is lost (fire, electronic fault, stolen, etc)? How would ...
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1answer
92 views

What key is used to encrypt the certificate and certificate verify message in TLS1.3?

Which key is used to encrypt certificate and certificate verify message in TLS1.3? I could not figure out which one it is reading section 4.4.2 of RFC 8846 and I only saw a vague mention on page 11.
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CAs are pre-loaded on the system, but how is it able to get intermediate certs?

I have the following X509 certificate: ...
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Parsing of X.509 certificates

I'm working on a firmware for a platform with limited resources with C as programming language. There are a set of cryptographic primitives to be implemented, including AES, GCM/GMAC, ECDSA, ECDH. ...
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1answer
931 views

How android apk file signing works?

There are a number of pages on web to tell how to sign apk file for Android. But none I've found telling how it works under-the-...
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864 views

Can I apply “encrypt with public key and decrypt with private key concept” using ECC certificate?

If Alice wants to send encrypted message to Bob, she can use Bob's public key to encrypt the plain message. Once Bob reliably gets encrypted message, he can decrypt it with his private key. In this ...
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Is there a method/protocol to validate a self-signed certificate by comparing a shortened hash?

I'm working on a solution where an iPad should connect to a server software running on a laptop using TLS with a self-signed certificate that was automatically generated on the laptop during the ...
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Authenticating code securely and generating a certificate

I'm working on a product with strong security. Essentially there is an App, downloaded from the iTunes App Store. When the App starts up, it generates a strong RSA keypair and stores it in the ...
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1answer
670 views

How to identify RSASSA-PSS from rsaEncryption OID?

Following the RFC 8446 it states that: RSASSA-PSS RSAE algorithms: Indicates a signature algorithm using RSASSA-PSS [RFC8017] with mask generation function 1. The digest used in ...
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1answer
577 views

Find hash and signature algorithms used in an X.509 certificate signed with RSASSA-PSS

I'm trying to understand the new PSS scheme, but having trouble figuring out how to parse it properly. When receiving a certificate with OID of RSASSA-PSS, how can I know which hash and signing ...
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1answer
654 views

How to generate a certificate/PEM from specific plain text keys?

Is there a way to generate a certificate with a pre-stablished public/private plaint text keys? Explaning: I generated some keys on a web site for development propurses, but now one of the parties ...
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1answer
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RSA certificate needed in CVC format

I had a client requirement asking me to provide an existing base64 encoded certificate in a CVC format. Could someone point me in the right direction here to understand what this format is? How can I ...
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1answer
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What is the maximum length of a X.509 OID?

I'm working on a feature for a project to determine if a given X.509 certificate is an EV Certificate, and if so, who is the authority behind that certificate. To do this, I grabbed the list of EV ...
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1answer
131 views

Any case that can require to encrypt a certificate revocation list before distribution

As far as we know certificate revocation lists (CRLs) include public information so they do not have to be encrypted before distribution. Is there a case that can require to encrypt it before ...
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1answer
162 views

Would SHA-1 be safe for certificates with short validity?

There are articles floating around the topic of SHA-1 deprecation. The gist of it is that in (mostly) developing countries, people are still using mobile/computing devices that are 5 years old (or ...
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Certificate for the public key

I am new to Network Security and learning about various security features like Diffie-Helmann and others. I understand that the Public key send by the server to the client needs to certified that it ...
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1answer
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Enforce weak RSA in TLS

I'm going to give a small talk on the mathematical background of RSA. My audience will consist mostly of software engineers and to make the mathematical stuff tangible, I wanted to demonstrate how to ...
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How can Bob validate Alice’s certificate?

Suppose that Alice has a certificate CA1 << Alice >> issued by the certification authority CA1, and Bob has a ...
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What data Certificate Authority encrypt for CSR?

I have been searching for a detailed explanation but can’t seem to find a low level one. 1) When CA sign the data with its private key, the encrypted data is APPENED to the csr or the whole cert ...
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1answer
253 views

CRL number generation sequence: can I use a time stamp?

RFC 5280 states that the CRL number should monotonically increase. I have seen this common practice of incrementing the CRL number by 1, every time a new CRL is generated. But can I use a Unix (epoch ...
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1answer
574 views

Reusing PGP key when generating SSL Certificate Authority?

Does it make sense to reuse some of the keys from my PGP (gnupg, gpg) keyblock when generating my own SSL Certificate Authority (a toy one for myself and a few web services of mine)? In an ideal ...
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524 views

Digital Certificate Chain Verification

Does a certificate contain the complete chain of all certificates up to the trusted root certificate, or does the program that verifies certificates have to fetch each parent certificate individually ...
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2answers
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What exactly is the contents of the LDAP userSMIMECertificate attribute?

I'm trying to setup an LDAP with user certificates. I have already learned that certificates can be stored in either the userCertificate attribute in DER format, or ...
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1answer
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Secure scheme to share symmetric key using asymmetric keys and certificates with N parties

I need to distribute symmetric AES key into number of end points which will use it to decrypt data. The AES key will be the same on all end points, it is not possible to generate unique on every end ...
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1answer
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X.509 strong authentication protocols

Is there also a protocol definition in X.509? In "Handbook of Applied Cryptography" by A. Menezes there is a reference to X.509 strong authentication protocol, nevertheless, I could not find the ...
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1answer
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X509 CertificatePolicies, IssuerAlternativeNames, BasicConstraints extensions. What is done when Issuer signs?

I have got one theoretical question related to extensions of X509 Certificate. More precisely I have question about what is happening when issuer signs subject's certificate with has several ...
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1answer
490 views

Why does Apple create a certificate for my push notification key [closed]

Brief rundown of how Apple Push Notifications (APN) work: Generate a keypair, generate a CSR for it Upload the latter to your Apple Developer account and associate it with your mobile app In the ...
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1answer
169 views

How to pass an arbitrary signature to a certificate

I am trying to sign certificate (X509) using secret sharing. That is shareholders combine their signatures to produce the final signature which will be in this case the signed certificate. However ...
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1answer
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Verification of identity by certification authority

I have question about how a user's identity is verified by a Certification Authority. As I understand it, the process works as follows: User generates his private key and (with the help of private ...
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1answer
674 views

Generate an insecure public / private key pair

I am looking for a way to generate an "insecure" public key pair. and by insecure I actually mean a pair that is breakable using brute-force (or other encryption) methods. As far as I know PGP ...
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1answer
664 views

PKCS12 password of container and private key

As I understand pkcs12 defines a container structure that can hold both a certificate and one or more private keys. ...
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What security is provided by a certificate? [closed]

I've been working on the topic of certificates for a little while, and here is what I understand: A certificate is basically a public key + some data about the owner of the certificate + a signature ...
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1answer
97 views

How does a receiver treat X.509 self-certificate with unknown the Signature Algorithm ID?

As I know X.509 self-certificate is a mechanism that the host generates public and private keys, the public key will insert to a certification and the private key will be used to sign the ...
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1answer
284 views

Revoke a GPG key using previously generated revoke certificate after renewd (change expiration date)

I have few sub-questions Do secret keys get expired, or just the public key gets expired? Do I have to back up the master sec key each time I renew it? For an ...
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Compromised Issuing CA [closed]

I'm configuring a PKI infrastructure with an offline root CA and several issuing CAs. Among other topics, I'm struggling to decide how the revokation of an Issuing CA certificate works. My Root CA ...
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1answer
136 views

x509 CA trust question

I'm trying to understand the logic of CAs, trust and client certificates. I have a general understanding but am having a tough time bridging some gaps. In a hypothetical situation a software system ...
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Creating colliding x509 certificates: Crafting RSA moduli step

I am trying to generate 2 x509 certificates with the same signature but different values in the common name field, based on md5 collisions, as it was specified in this paper (page 7). Now I have ...
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Is Common Name encoded in the certificate?

When I make a certificate like so cd /etc/openvpn/easy-rsa/2.0/ source ./vars . /etc/openvpn/easy-rsa/2.0/build-key client1 Then ...
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Digital Certificates genereted from Hardware Security Module

Software library without hardware based source of entropy will provide enough security to generate digital certificates. However Hardware security Modules provide hardware based source of entropy and ...