Openssl

OpenSSL is an open source software system that provides the following:

• Forensic-grade implementations of the most widely used hash functions.
• Symmetric cryptographic functions
• Asymmetric cryptographic function
• Certificate management functions
• A complete S/MIME implementation
• A complete SSL/TLS implementation

OpenSSL is interesting for forensic practitioners and developers because it provides a basic toolkit for building software, and because the higher-level certificate management functions give you an easy way to decode the contents of certificates that are used to secure computer systems.

This web page contains step-by-step instructions on using OpenSSL from the command line to perform specific tasks. There are a lot of online OpenSSL guides and we'll try to link to some of them from here. But this page is a handy reference just the same.

File Extensions

OpenSSL doesn't care what you use for file extensions. However, the following extensions to seem to be commonly used:

File Extension	Meaning
.pem	can contain a private key, public key, or certificate signing request
.crt	Windows file extension for a .pem file
.p12	a PKCS12 file, which contains a private key and a certificate, encrypted for transport with a passphrase. This is the format that Windows and MacOS like to import