Is x509 same as PEM?

What certificate formats are x509?

I was looking at the cert file of my browser and found that it is in x509 format.

What is this format? Is it a special format that I can use to create my own certificates or is it just another format that browsers use for their own certificates? A certificate in X.509 format is actually a signed certificate that has been "signed" by a CA that is trusted by a browser or other trusted party. The public key of the certificate is normally encoded as a DER-encoded X.509 certificate (a X.509 certificate is made up of three parts, the subject, issuer, and serial number) that is signed by the CThe basic idea behind the signature is that the CA is telling you that the certificate is valid, that it was issued by them and that the person who signed the certificate is known to them. The actual algorithm used to sign the certificate is an X.509 v3 certificate signed with SHA1 as the hash algorithm.

In order to make use of the certificate, a client must trust the CA, which can be done using a certificate chain. The certificate chain is a chain of certificates in which the end certificate of the chain is the one you want to use.

What does a x509 certificate contain?

It's not the "what", but more of "why" and "where" it is used.

When you want to communicate with a remote server, you need to be able to prove that you are the true source of the message that you're sending. To do this, you use X.509 certificates, which are a way of digitally signing and identifying data.

What does it contain? Information about who you are (and sometimes where). A public key that you can use to verify that the information you are sending is really from you. A digital signature of the certificate that you send. This signature is made up of a bunch of random data that is used to identify the certificate, and the hash of some data (the "message") that you are sending Note that certificates are also used in other contexts. Some web sites will ask for your certificate to prove that you are who you say you are, to verify that you are a real human. They do this because they may want to be able to revoke your certificate at any time if they discover that you are not who you said you were.

Some web sites also use a self-signed certificate in a similar fashion. In these cases, you're not directly communicating with the web site, so there is no requirement to trust that you are who you say you are.

Some web sites use a different type of certificate called an EV certificate, which proves that you are who you say you are, and that you can be relied upon. Where are they used? When communicating with a remote server. In digital signatures, which include things like public keys and digital signatures. Why should I care about them? You might want to have your own certificate to prove that you are who you say you are on your own web site. If you have a business relationship with a web site, it may be important that they know that you are who you say you are. Some web sites may even require you to use their services in order to be verified as who they claim you are.

What is x509 structure?

To understand the structure of x509 certificate, you should first understand what an ASN.

1 structure is.

X.509 Certificate Structure ASN.1 is one of the most commonly used methods of representing data on the web. Most data represented on the internet has some sort of ASN.1 representation. For example, XHTML is encoded using ASN.1 whereas HTTP requests and responses are encoded using ASN.

In general, ASN.1 is used to represent a set of elements in a serialized binary format. In order to define an ASN.1 structure, a notation called BER (Base Encoding Rules) is used.

As mentioned earlier, x509 certificate is encoded using ASN. Let's go through the key elements of x509 certificate, starting from the certificate attributes, and move forward to each element in the certificate.

Certificate Attributes. The certificate attributes have different names for different fields. They can be encoded using BER.

For example, the CN (Common Name) attribute has a BER encoding of OID (Object ID) while the EmailAddress attribute has a BER encoding of RDN (Relative Distinguished Name). These attributes are always encoded first.

Before we go into the details of encoding each element in the x509 certificate, let's discuss how they are grouped. Grouping of Certificate Elements. Generally, there are three types of grouping involved in x509 certificates. Namespaces Grouping. Attributes Grouping. Certificate Groups. Let's first look at the namespaces and attributes groupings. Namespace Grouping. All the objects that you need to encode using ASN.1 are put into a single namespace. For example, the x509 certificate contains a single object that's known as the Certificate object. All the attributes and elements of a certificate belong to this single object, which is known as the Certificate object.

Namespace grouping helps in making the objects clear, but it also has some issues. As shown in the figure above, there are several objects within a single namespace that are not related to each other. This makes it difficult to know the relationships between these objects.