Questions tagged [x.509]

X.509 is a standard for a public key infrastructure used for authentication and access control. X.509 specifies standard formats for certificates, revocation lists, attribute certificates, and path validation.

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Which attributes in the subject of a X.509 certificate from a certificate authority are used as the "identifier"?

I've been trying to follow certificate chains of random websites I visit and see if I do indeed find them in my Windows 10 trusted root certificate authority store. I almost never find an exact match,...
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Is the Extended Key Usage extension mandatory on the web?

Do web servers reject certificates that do not have an extended key usage with TLS WWW Client Authentication set (if client authentication is required)? Similarily, do Browsers reject certificates ...
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Definitions for CRL Reasons

Is there any authoritative definition of the various reasons possible in a CRL file? Section 6.3.2(b) of RFC5280 lists a few: unspecified keyCompromise cACompromise affiliationChanged superseded ...
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Why does Digicert have so many Root Certificates? Which one is right for me?

I'm trying to add a system root certificate to a container that doesn't have any. Digicert is a CA that I've used before, but I've never had to add a root certificate to my system before. Then I ...
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What's the policy of CAs for validity period of certificates?

Let a CA generate a new X.509 certificate for the web. I wonder about the rules for the validity period: (Q1) On what does the validity period depend on ? (Q2) Does it depend on the pricing model ...
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Converting .pem to .key file

I downloaded certificated for my website using letsencrypt: letsencrypt -d crackerscreed.me --manual --preferred-challenges dns certonly The process was successful but the site I want to implement ...
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483 views

Can I re-sign SMIME certificates with my own CA?

Many large corporations choose to use their own CA to sign their employee's SMIME certificates. Which is fine for internal use, but they typically expect external users to import their corporate CA ...
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584 views

Generate X509 ERR_CERT_COMMON_NAME_INVALID

I am trying to set up https server on python3, but I could not generate a certificate and a key properly. That is the server code: import http.server, ssl server_address = ('localhost', 4443) httpd =...
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Why did RFC 4158 (Path Building) restrict Trust Anchors to self-signed certificates?

I'm having trouble using Wget to download a file over HTTPS from ftp.gnu.org using the Let's Encrypt X3 root. The Let's Encrypt X3 is cross-certified, which means it has an issuer and its not self-...
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Mutual auth client certs for a pool of requesting servers behind a proxy

I've got a situation that is puzzling me. We have a vendor that is requiring mutual authentication when making a request to them. They are requesting we give them a client cert identifying our ...
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Missing 'Key Usage' on a CA certificate: can sign certificates?

In Windows certificate store, an intermediate CA certificate without Key Usage extension is considered eligible (as long as it has isCA flag from Basic Constraints of course) for singing end entity ...
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746 views

Not supported critical extensions

I've read the great post written by @Thomas Pornin Which properties of a X.509 certificate should be critical and which not? and it raised my question. STORY: Let's assume that I have a client C ...
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Is it possible to add an x509 extension to a certificate after creation?

I'm under the impression that x509 extensions must be added at certificate creation time. Just want to check that my understanding is correct and that I can not take a certificate after it was created ...
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CA with lower key size than issued certificates

If a root certificate has a 2048 bit key is it correct to assume that if a certificate request signs a request made by a 4096 bit key and generates a certificate that the security has been weakened to ...
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What is the meaning of public key parameter in the X.509 certificate?

While I am checking the fields of X.509 I've noticed there is field called public key parameter and its value is 05, what is the use of this field? I have searched and did not find a clear answer for ...
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Certificate Transparency: Log a legit precertificate and issue a rogue certificate

I'm trying to understand how Certificate Transparency solves the problem with dishonest Certificate Authorities embedding an SCT in their certificates. I understand that the log is append-only, and ...
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File signed with maliciously installed certificate on machine

Let's assume we have a system delivering files (such as updating a program) that are digitally signed with a trusted CA. If an attacker somehow manages to install custom certificate as a trusted ...
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Why is there no certificate error while visiting google.net although it presents a certificate issued to google.com?

The following output shows that google.net is presenting a certificate that has been issued to www.google.com. $ openssl s_client -connect google.net:443 < /dev/null > out.txt 2>&1; cat ...
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Is it possible to create GnuPG keys from a x509 cert/key pair?

I have a digital cert issued by my organization for signing email. It's imported into Thunderbird and the key and cert can be exported to a .p12 from within Thunderbird. I'd like to use the .p12 to ...
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Can an SSL certificate be used to generate a SAML token

An external application (B) requires a SAML token to allow users who log into my application (A) to access it directly without having to log in again. This access is not built yet. My organization has ...
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Self Signed SSL Certificate - How to verify it correctly on the client side?

For our current implementation we are using a self signed root certificate, which then is used to sign ssl certificates for our secure http connection. My question relates to the verification logic ...
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What is a KEA certificate and how it is used?

I'm currently studying IKE and IPsec in the context of VPN applications and I know that a X.509 certificate is used to provide server's public key to the client (and vice-versa in case of mutual ...
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What's the state-of-the-art approach to secure a backend API?

Scope Currently we are developing a backend REST API which is consumed by handful of MVC applications. In this case we are talking only about server-server communication and the API won't be consumed ...
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How is a certificate extension different from a certificate file name extension?

The following article has explained both differently. X.509 wiki Now my question is: Can we use more than one extension in a certificate? Is it how there can be more than one use of extensions in a ...
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170 views

Is the windows root trust store used by IE?

With the Symantec-Google drama, it would help to know if the Internet Explorer browser has its own root trust store built in to the browser, or uses the automatically updating Windows System root ...
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ASN.1 encapsulated BITSTRING type in openSSL

I am currently building an ASN.1 parser which supposed to decode X.509v3 certificates and epoch files in ASN.1 DER format. The parser is working well apart from one issue which I couldn't seem to get. ...
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Verification and authentication flow for X509 code-singing certificate

I am developing an embedded devices FW updates (not connected to the internet) and I am using code-signing certificates in order to verify the FW update issuer identity (the FW update is signed with ...
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CA signature algorithm vs certificate public key algorithm

Is there any restriction on the CAs signature algorithm with respect to the public algorithm in the actual server/device certificate? For example, can a ECDHE_ECDSA_* certificate be signed by a CA ...
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Why does generating a self-signed X509 certificate not require my public key?

Let's say I have an RSA (2048) keypair that I generated private.key public.key For testing purposes I'd like to generate a self-signed X509 certificate. My understanding of a certificate is that it ...
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Can X.509 Authentication be subject to brute force attacks?

I am working on an application (using Spring Security) that has two possible user authentication mechanisms: either X.509 certificate (using mutual SSL handshake) or user + password For user+...
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IP address in SubjectAltName

Is it allowed to specify IP as DNS name for SAN certificate ?
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Building a "Hello, world!" X.509-based system for establishing trust between servers

I want to build a distributed software system with the following elements: A number of workers, which manage potentially sensitive data and execute code on behalf of a number of clients. A number of ...
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Does X.509v3 certificates prevent MITM attacks in SSH

I was reading RFC 4251 (really all of the SSH RFCs) and in section 9 it goes into great length about security considerations listing 3 cases of MITM attacks. In several places in the RFCs the authors ...
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Signature in ECDSA-signed X.509 certificates

I wonder if there is a standard way of encoding the ECDSA-signature in the signature field of an X.509 certificate. As far as I understand, the signature is a tuple of two integers r and s. If the ...
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At which offset is the public key in an DER encoded certificate chain?

I have the following bytes array storing a certificate chain (DER encoded): ...
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Why Signature Hash Algo SHA-1 still uses for X509 by GeoTrust [duplicate]

Google has successfully shattered SHA-1 and still I found that SHA-1 digest algorithm is used for signing the hash. Even Google Chrome is accepting this kind of certificate without any kind of warning....
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Correct settings to generate private intermediate CA

I am using 'xca' in Linux to set up a private CA. xca only includes templates for the Root CA and End-User CA, no intermediates. What are the correct settings (fields and flags) for an intermediate (...
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How to get public prime from DHE from TLS v1 DHE-RSA x.509 certificate?

I can view the certificate using openssl s_client -showcerts -connect www.masaood.com:443 </dev/null I can view the public key of a RSA, but cannot find any information for DHE: openssl ...
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X.509 Why is the signature algorithm added twice in the Attribute Certificate?

As I read some parts of the X.509 specification I found the signature added twice - first in the AttributeCertificate as signatureAlgorithm and second in the AttributeCertificateInfo as signature. ...
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Verify that a second TLS connection comes from the same client

I would like to implement kind of a trust-on-first-use (TOFU) scheme with TLS: A client creates a key and a self-signed certificate. The client connects to the server with this certificate. The ...
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WPA2 Enterprise EAP-TLS Key Exchange

I'm in the process of implementing 802.1x WPA2 Enterprise Authentication using FreeRadius and EAP-TLS (Mutual TLS Cert Based Auth). I am keen to understand how to actual protocols work together and ...
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X.509 certificate renew vs. rekey

What is the difference from CA perspective between renewal and rekeying of the certificate previously issued by this CA?
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RSA or ECDHE for key establishment?

Recently, i have been looking at PKI and certificates, and TLS 1.2 as part of my study of cryptography. I have the understanding that the public key included in the certificate of a website is the key ...
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RSA or ECDHE for x.509 certificates-what does each do?

I am relatively new to x.509 certificates, but recently i have been looking at the https connection padlock at the top of the screen. On certain websites, clicking on the pad informs me that the site ...
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Missing X509 extensions with an openssl-generated certificate

My goal is to create a certificate with opensslsimilar to this one generated with cfssl Certificate: Data: Version: 3 (0x2) Serial Number: 60:44:dc:0d:80:f4:54:55:e8:...
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Could governments and banks become CAs?

When you apply for a passport, driver's license, home mortgage, bank account, credit card, etc., the issuing organization must verify your identity. In the course of doing so, would it be feasible for ...
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How are ECDSA signatures computed for X509 Certificates?

I am trying to verify a certificate signature on my own. To do this, I created a self-signed certificate using OpenSSL with the two following command lines: openssl ecparam -name secp256k1 -genkey -...
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Using short hostname in X509 certificates

We are using an internal Certificate Authority for our company. We noticed that it is possible to add as subjectAltName the hostname without the domain. We are using example.org for internal servers ...
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OpenSSL Verify: Difference Between "unable to get issuer certificate" and "unable to get local issuer certificate"

From the man pages: 2 X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT: unable to get issuer certificate the issuer certificate of a looked up certificate could not be found. This normally means the ...
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How to restrict a X509 certificate to be used only for a web server

I would like to restrict the X509 certificate for a site to be used strictly for a web service, as opposed to code signing or certificate signing. Which basicConstraints and keyUsage usage attributes ...

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