Create Self-Signed SSL Certificates in Your Browser Generate self-signed SSL/TLS certificates for development.

The tool uses the Web Cryptography API to generate an RSA key pair, specifically utilizing the RSASSA-PKCS1-v1_5 algorithm with a SHA-256 hash function. This is achieved through the `crypto.subtle.generateKey` method, which takes in parameters such as the algorithm name, modulus length, and public exponent. The generated key pair consists of a private key in PKCS#8 format and a public key in SPKI (Subject Public Key Information) format. To create the certificate, it constructs an info string containing details like subject, issuer, validity dates, and the base64-encoded public key.

The `ab2b64` function is used to convert the ArrayBuffer representation of the public key into a base64-encoded string, which is then formatted according to the PEM (Privacy-Enhanced Mail) standard. The `fmtPem` function takes in this base64 string and wraps it in the necessary headers and footers to create a valid PEM-formatted certificate or private key. For example, when generating a certificate with a subject CN set to "localhost", the tool will produce a PEM-formatted certificate containing lines like "-----BEGIN CERTIFICATE-----" and "-----END CERTIFICATE-----". The same process is applied to the private key, resulting in a PEM-formatted private key that can be easily copied and used in development environments.

The validity period of the generated certificate is determined by the number of days specified by the user, with a default value of 365 days. This period is calculated using JavaScript's Date object, which provides methods for manipulating dates and times. The resulting certificate contains the validity start and end dates in ISO format, as required by the PEM standard. Upon generation, both the certificate and private key are displayed in text areas, allowing users to easily copy them to the clipboard using the `copyToClipboard` function from the `@/lib/utils` module.

In terms of security, the tool's use of RSASSA-PKCS1-v1_5 with SHA-256 provides a secure method for generating digital signatures. The adjustable key sizes of 2048 or 4096 bits also allow developers to balance security and compatibility according to their needs. Overall, the combination of Web Cryptography API, PEM formatting, and JavaScript date manipulation enables the tool to generate self-signed certificates that meet common development requirements.