You need to encrypt some sensitive data for transmission over the internet or storage on disk, but you don’t want anyone else to be able to read it without your permission. And then suddenly, you realize that you have no idea how to use OpenSSL!
In case you haven’t heard of it before, OpenSSL is an open-source cryptographic library that provides various protocols for secure communication over the internet. It supports a wide range of encryption algorithms such as AES (Advanced Encryption Standard), RSA (RivestShamirAdleman), and DH (DiffieHellman).
Now, some basic concepts that you need to understand before we dive into the details. First of all, what is encryption? Encryption is the process of converting plaintext (readable text) into ciphertext (unreadable text), which can only be decrypted by someone who has a secret key or password. This ensures that your data remains confidential and cannot be intercepted by unauthorized parties.
Next, keys. Keys are the backbone of any encryption system they allow you to encrypt and decrypt data using specific algorithms. There are two types of keys: public and private. Public keys can be shared with anyone who needs them (e.g., for secure communication over the internet), while private keys should be kept secret at all times (e.g., for signing digital documents).
Now that we’ve covered some basic concepts, let’s move on to our first example: encrypting a file using OpenSSL. To do this, you can use the following command in your terminal or console window:
openssl enc -aes-256-cbc -in plaintext.txt -out ciphertext.bin -pbkdf2 -pass "pass:mysecretpassword"
This will create a new file called `ciphertext.bin`, which contains the same data as your original file (`plaintext.txt`) but in an encrypted format. The `-aes-256-cbc` option specifies that we want to use AES encryption with 256-bit keys and CBC mode, while the `-pbkdf2` option tells OpenSSL to use a password-based key derivation function (PBKDF2) for generating our secret key.
Now decryption how do we get back our original file from this encrypted mess? Well, it’s actually pretty simple: just run the following command in your terminal or console window:
# This script uses OpenSSL to decrypt a file that has been encrypted using the AES-256-CBC algorithm.
# The -d option specifies that we want to decrypt the file.
# The -in option specifies the input file, in this case "ciphertext.bin".
# The -out option specifies the output file, in this case "decrypted_plaintext.txt".
# The -pbkdf2 option tells OpenSSL to use a password-based key derivation function (PBKDF2) for generating our secret key.
# The -pass option specifies the password to be used for decryption, in this case "mysecretpassword".
openssl enc -d -aes-256-cbc -in ciphertext.bin -out decrypted_plaintext.txt -pbkdf2 -pass "pass:mysecretpassword"
This will create a new file called `decrypted_plaintext.txt`, which contains the same data as your original file (`plaintext.txt`) but in its original format. The `-d` option specifies that we want to decrypt our ciphertext, while the other options are the same as before.
Now some more advanced concepts like key management and certificate signing. But for now, let’s just say that these features allow you to securely transmit data over the internet using SSL/TLS (Secure Sockets Layer/Transport Layer Security) protocols. And if you want to learn more about them, well…you know what to do!
Later!