Public Key Infrastructure | Cryptography

Introduction to Public Key Infrastructure (PKI)

Public Key Infrastructure (PKI) is a framework that provides secure communication over networks using public key cryptography. It involves the use of digital certificates, certificate authorities (CAs), and registration authorities (RAs) to verify and authenticate the identities of entities in a network.

PKI is essential for establishing trust in electronic transactions, enabling secure email communication, and ensuring the integrity and authenticity of software updates.

Components of PKI

PKI consists of the following key components:

Public and Private Keys: A pair of cryptographic keys used for encryption and decryption. The public key is shared openly, while the private key is kept secret.
Digital Certificates: Electronic documents that bind a public key to an entity's identity, issued by a Certificate Authority (CA).
Certificate Authority (CA): A trusted entity that issues digital certificates and verifies the identity of certificate requesters.
Registration Authority (RA): An entity that assists the CA by validating the identity of entities requesting digital certificates.
Certificate Revocation List (CRL): A list of revoked certificates that are no longer trusted.

How PKI Works

PKI works through the following steps:

Key Generation: The entity generates a pair of cryptographic keys (public and private).
Certificate Request: The entity submits a certificate signing request (CSR) to the RA, which includes the public key and identity information.
Identity Verification: The RA verifies the identity of the entity requesting the certificate.
Certificate Issuance: The CA issues a digital certificate binding the public key to the entity's identity.
Certificate Distribution: The digital certificate is distributed to the entity, which can now use it for secure communication.
Certificate Validation: Other entities can validate the certificate by checking its authenticity and validity using the CA's public key.

Example: Generating a Digital Certificate Using OpenSSL

Let's walk through an example of generating a digital certificate using OpenSSL, a popular open-source cryptographic toolkit.

Step 1: Generate a Private Key

Run the following command to generate a 2048-bit RSA private key:

openssl genpkey -algorithm RSA -out private.key -pkeyopt rsa_keygen_bits:2048

Generating RSA private key, 2048 bit long modulus
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e is 65537 (0x010001)

Step 2: Create a Certificate Signing Request (CSR)

Run the following command to create a CSR using the private key:

openssl req -new -key private.key -out request.csr

You will be prompted to enter information about your organization. The output will look something like this:

Country Name (2 letter code) [AU]:US
State or Province Name (full name) [Some-State]:California
Locality Name (eg, city) []:San Francisco
Organization Name (eg, company) [Internet Widgits Pty Ltd]:Example Corp
Organizational Unit Name (eg, section) []:IT
Common Name (e.g. server FQDN or YOUR name) []:example.com
Email Address []:admin@example.com

Please enter the following 'extra' attributes
to be sent with your certificate request
A challenge password []:
An optional company name []:

Step 3: Generate a Self-Signed Certificate

Run the following command to generate a self-signed certificate valid for 365 days:

openssl x509 -req -days 365 -in request.csr -signkey private.key -out certificate.crt

Signature ok
subject=C = US, ST = California, L = San Francisco, O = Example Corp, OU = IT, CN = example.com, emailAddress = admin@example.com
Getting Private key

Conclusion

Public Key Infrastructure (PKI) is a vital component of modern cybersecurity, providing the foundation for secure communication and trust in digital transactions. By understanding the components and processes involved in PKI, you can better appreciate its importance and effectively implement it in your organization.

Public Key Infrastructure (PKI) Tutorial