Glossary of PKI Terms


Asymmetric Cryptography

In this Cryptography a Key Pair - Private and Public Key is used. Private Key is kept secret and the Public Key is Widely distributed.



A Data Record that contains the information as defined in the X.509 Format.

Certificate Authority (CA)

Issuer of the Digital Certificate. Also validates the Identity of the End-Entity that posseses the Digital Certificate.

Certificate Signing Request (CSR)

Certificate Signing Request (CSR) is what you send to a Certifiate Authority (CA) to get enrolled. A CSR contains the Public Key of the End-Entity that is a requesting the Digital Certificate.

Common Name (CN)

Common Name is the name of the End-Entity e.g. Saqib Ali. If the End-Entity is a WebServer the CN is the Fully Qualified Domain Name (FQDN) of the WebServer


Digital Certificate

A certificate that binds a Public Key to a Subject (end-entity). This certificate also contains other indentifying information about the subject as defined in the X.509 Format. It is signed by Issuing CA, using CA's pivate key. e.g. of a digital certificate

Digital Signature

A Digital Signature is created by signing the Message Digest (Message Hash) using the Private Key. It ensures the Identity of the Sender, and the Integrity of the Data.



An entity that participates in the PKI. Usually a Server, Service, Router, or a Person. A CA is not a End-Entity. An RA is an End-Entity to the CA



A hash is Hexadecimal number generated from a string of text such that, no two different strings can produce the same hash.

HMAC: Keyed Hashing for Message Authentication

HMAC is an implementation of Message Authentication Code Algorithm.


Message Authentication Code

Similar to a Message Digest (Hash/Fingerprint), except the Shared Secret Key is used in the process of calculating the Hash. Since a shared secret key is used, an attacker can not change the Message Digest. However the shared secret key has to be first communicated to the participating entities, unlike Digital Signature where Message Digest is signed using the Private Key. HMAC is an example of a Message Authentication Code Algorithm.

Message Digest 5 - MD5

Message Digest 5 (MD5) is a 128-bit one-way hash function


Private Key

Private Key is the Key in Asymmetric Cryptography that is kept secret by the owner (End-Entity). Can be used for encryption or decryption

Public Key

Public Key is the Key in Asymmetric Cryptography that is widely distributed. Can be used for encryption or decryption

Public Key Infrastructure (PKI)

Public Key Infrastructure


SHA-1: Secure Hash Algorithm

Secure Hash Algorithm (SHA-1) is a 160-bit one-way hash function. Maximum message is 2^64 bits.

Secure Socket Layer (SSL)

Secure Socket Layer (SSL) is a security protocol that provides authentication (Digital Certificate), confidentiality (encryption), and data integrity (Message Digest - MD5, SHA etc).

Symmetric Cryptography

In this cryptography the message the encrypted and decrypted by the same key. (((n^2-n))/2) keys are required for n users who want to participate in this system of cryptography.