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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Are there stenography benefits to a “n-prime”?

As mentioned in this StackOverflow CodeGolf question, prime numbers can be redefined: One of my favorite definitions of the prime numbers goes as follows: 2 is the smallest prime. ...
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865 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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Changing the public key in an MD5 certificate

Given a valid, signed X.509 certificate using the MD5 digest algorithm and an RSA public key, how feasible would it be to generate a public key which would, all other parts of the certificate being ...
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306 views

How can i verify a certificate to root? [closed]

I write some certificate Authority that has it's own private/public cert keys . This CA signs public keys of user. If for example i have user that has a public cert that signed by the CA. How I can ...
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Is it safe to include the public certificate in xml digital signatures?

My understanding of XML Digital Signatures: Let's use a SAML token as an example. Note - for the sake of simplicity I'm omitting some details like CanonicalizationMethod, base64 encoding, etc. In ...
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Can two different CA's/End Entities in different PKI's have the same asymmetric key pair?

Example: $X$ and $Y$ have the same asymmetric key pair. $X$ communicates with $A$ and gives it's PubKey to $A$. So, $A$ has the PubKey of $X$ which also happens to be the PubKey/PrivKey of $Y$. ...
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1answer
123 views

Is allowing both digitalSignature and keyEncipherment certificate usages a bad practice?

From what I see, many server and client RSA certificates in the real deployments have the "key usage" mask containing both digitalSignature and keyEncipherment. Isn't this a bad (that is, potentially ...
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Who issued the first SSL certificate?

When SSL was introduced in ~1996, there was only a few CAs issuing certificates for that specific use and a few sites which actually used SSL. Which Certification Authority issued the first SSL ...
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Certificate Master Public Key with Pairing

I am currently working on CipherText Policy Attribute Based Encryption (CP-ABE) scheme. If we see the scheme, we can notice that the Authority may generate a Master Public Key and a Master Private Key(...
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1answer
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Encrypted cerficiate signature for server certificate and intermediate certificate in packet capture

If we view the certificate chain using Firefox, we can see the certificate signature of "server certificate" and its "intermediate-CA" right after the "certificate signature algorithm" in the ...
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1answer
87 views

Direct Anonymous Attestation to replace CA

In term of authentication, I have the impression that to trust an entity it is mandatory to have a Certification Authority involve. Today I stumble upon an article something called Direct Anonymous ...
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Create broken chain certificates for testing

In our software we receive certificates in binary DER format from our clients. They are in advance used to perform certain identity checks between server and client. To ensure the certificates are ...
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Questions about the certificate authority procedures

I am beginner in cryptography and now I try to understand certificate process. I read this answer and have some questions about the enrollment process: The general procedure to issue certificates ...
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1answer
141 views

signature reconstruction in X.509 certificate with root private key

I created a root CA, let's say A. I created the Certificate Signing Request (CSR) for B, and get the certificate signed by A. I would like to know of what exact content the signature is made. This ...
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1answer
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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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3answers
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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 ...
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What exactly is inside a private key?

May sound stupid to many, but I would like to have some pointers on what exactly is contained inside a private key. I have decent understanding of public/private keys/certificates (have created them ...
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549 views

Why is a certificate needed at client side

I was wondering why you need a certificate of the server at client side. Can't you just fetch it from the CA itself? I am using mbedtls to program some small client, and in all the client examples ...
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How is OID 2a 86 48 86 f7 0d parsed as 1.2.840.113549?

I saw that an RSA key, created by OpenSSL, contains the following HEX string: 2a 86 48 86 f7 0d 01 01 01 that HEX string gets interpreted as Object ID: 1.2.840.113549.1.1.1 It is obvious 01 01 ...
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What is the most important piece of information in a X.509 certificate?

X.509 has a structure which contains information like version number, serial number, signature algorithm, issuer, subject name, subject public key, signature of the issuer etc. However, I'm having ...
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Signature verifying against multiple certified public keys?

I'm wondering if and how the current public key certificate infrastructure is guarded against the following scenario: Honest Alice obtains Eve's public key certificate Certe, made by honest CA Carol; ...
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Should a certificate be validated every time it is used?

In contrast to private keys, public keys don't need to be stored on a secure place. But what if somebody changes a certificate with a public key to just another one? To ensure certificate authenticity,...
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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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How to change the policy value of a CA identity in apple keychain?

According to this guide, I made an intermediate CA, and successfully used it to sign app in Windows. However, after converted it into a Apple keychain (by this guide), this CA become having an "iChat" ...
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How to configure a client browser cert to be authenticated by a server?

I currently am being asked to partake in a strange authentication format while working with a client, and was hoping for clarification. The client is using HTTPS with client certificate ...
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What does “G2” mean when used with X509 certficates and certificate authorities?

For example "Google Internet Authority G2"?. I thought it was another way of specifying Class 2 (for organizations, for which proof of identity is required) but then see certificates such as "VeriSign ...
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Raw signature of public key vs full certificate

I'm working on an device that will have its own keypair to sign data that it acquires. The public key will be signed with a provisioning key to ensure authenticity of the device. I want to put the ...
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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
736 views

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

So I am registering users and I need to know they really are who they say they are. More importantly that they represent the company they say they represent. I was told I can ask them to send me a ...
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1answer
537 views

Best practice to create certificate by CA

I suppose that I have this scenario: Root CA Intermediate CA Practice 1: The Root CA generates her own $PK_r$ and $PB_r$ key, and after it makes her certificate $Cert_r$. The Intermediate CA ...
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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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Why are some websites seemingly immune to self-signed certificate MitM attacks?

I recently did an experiment using MitM to gain account information (username and password) while accessing websites. I used two PCs in the scenario; one as the target, running Internet Explorer, and ...
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How can I validate a given Server-Certificate behind a HTTPS-connection?

I know more or less about how TLS works in principle. But how can I be sure, that the certificate behind a server's web site (e.g. tele-banking from my bank) has been issued to my bank and not to ...
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What is the correct format for a CRLF in a SSL certificate's pem

Currently I am working with SSL certificates inside a Ruby on Rails application. I am storing the certificates in a database along with the corresponding dhparam, and chain. At some point I want to ...
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858 views

Deduce modulus N from public exponent and encrypted data

This is an RSA question, given data encrypted with a public key from an unknown RSA certificate of 2048 bit, let $X$ be the encrypted data, $M$ the unencrypted data, $c$ the public exponent and $N$ it'...
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1answer
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How can a company have its own Certificate Authority for internal use?

It is possible for a company to deploy its own CA ? How would browsers accept the certificates ? Supposing a company does not want to use the role of a commercial server like Windows Server or any ...
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3answers
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Does the Shappening mean HTTPS can be broken?

For years we've been warned that SHA-1 is weaker than originally thought and should not be used. This reached its peak with the Shappening and experts from Schneier on down have been warning that we ...
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Certificate Authority RSA key expiration?

My understanding about SSL/TLS for HTTPS is that servers send their certificates to browsers and browser attempt to decrypt them using trusted CA public keys that are already presented in their store. ...
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Verification of Certificates in a Chain

The question is not about mathematical cryptography but about the practical usage of certificates and their chained verification. Please let me know, if this is the wrong place to post the question. ...
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1answer
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Certificate revocation

When someone claims that the private key corresponding to the public key has been stolen, and sends to the CA a statement of this fact signed with respect to public key pk. Why doesn't the CA need ...
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1answer
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Where x509 signature validation is concerned, what does the error “x509 certificate chain incomplete of leaf TP not found” mean? [closed]

I'm validating the x509 signature of an XML document and I encounter the following error: "x509 certificate chain incomplete of leaf TP not found" Any thoughts on what the impact is for a TLS ...
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2answers
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Are there example certificates available for test purposes?

Are there example certificates (PEM format) for testing available somewhere ? For test purposes I would need a certificate signed with SHAS256/ECDSA P-256, together with a complete chain to test ...
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1answer
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How is the PKCS #10 signature generated?

I'm generating certificate signing request in iOS, which does not provide proper ready-made API for CSR generation. Now the library I have used for CSR generation produces the different signature for ...
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1answer
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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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1answer
132 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
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Same certificate for server authentication and authorizatoin in other system

I have a program which acts as a node in a larger system. Those nodes can be connected to form a tree. TLS with mutual authentication is required, which means that each node has it's own certificate. ...
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2answers
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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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Method to verify a signed archive's X.509 CoT

I am trying to understand the key high level details behind verifying trust when downloading an archive. This is my understanding of how it could be done: On the Software Developer side: Obtain a ...
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1answer
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Is there a way to inercept encrypted https connections by mimicking a cert authority?

In this video, it is shown how encryption can be theoretically intercepted without the client noticing it. In short something in between the connection could make a handshake with the requested ...
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1answer
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RSA and ECDSA Certificate Sizes

Is there a table (or a whitepaper from official sources) that compares the size of X509 certificates generated with RSA (starting from 1024 bits) and ECDSA (starting from 160 bits) ? Thanks for the ...