SSL & TLS 3: AES and RSA (2024)

Prateek Bansal

I. Introduction

AES is a symmetric key encryption cipher, and it is an iterative rather than Feistel cipher. It is widely used across the globe to protect sensitive data.

2. Technical Definition

AES is a block cipher that encrypts data in fixed-size blocks (128, 192, or 256 bits) using the same key for both encryption and decryption. This key must be shared and kept secret between the two parties.

3. Easy Definition

AES is like a safe lock that uses the same key to both lock (encrypt) and unlock (decrypt) the safe. Everyone who needs access to the contents of the safe must have a copy of the key.

4. Analogy to Understand

Consider AES encryption as a complex puzzle box. You arrange the contents inside the box and use a specific pattern to close it, which is known only to you and the recipient. When the recipient gets the box, they use the same pattern to open it and access the contents.

5. Example of Real Life Where This Concept is Used

AES is used when you shop online and enter your credit card information. The information is encrypted with AES before it is sent over the internet to the merchant, protecting it from being intercepted and read by unauthorized parties.

I. Introduction

RSA is an asymmetric cryptographic algorithm used widely for secure data transmission. Unlike AES, it uses a pair of keys; a public key for encryption and a private key for decryption.

2. Technical Definition

RSA works on the principle of factorizing large integers that are the product of two large prime numbers. The public and private keys are generated together using these prime numbers in a way that ties them together mathematically.

3. Easy Definition

RSA is like a mailbox with a slot and a key. Anyone can drop a message through the slot (encrypt with the public key), but only the owner of the mailbox can open it and read the messages (decrypt with the private key).

4. Analogy to Understand

Imagine you have a special padlock with two keys: one to lock (public key) and another to unlock (private key). You can give the locking key to anyone to secure a box, but only you have the unlocking key, so only you can access what’s inside.

5. Example of Real Life Where This Concept is Used

RSA is often used to encrypt a session key which is then used for AES encryption of data. This allows for a secure exchange of the AES key. It’s commonly used in scenarios like HTTPS connections for secure web browsing, where the RSA algorithm establishes a secure channel.

Both AES and RSA are essential for protecting data in the digital world, but they are used differently depending on the requirements of confidentiality, integrity, and authentication. RSA is useful for establishing secure connections and securely exchanging keys, while AES is efficient for the high-speed encryption of large volumes of data.

To encrypt and decrypt data using AES and RSA, you can use various command-line tools, such as OpenSSL, which is available for Linux, Unix, MacOS, and Windows (via Cygwin or a similar compatibility layer). Below are the command-line examples for both AES and RSA encryption:

Encryption with AES:bashCopy code

openssl enc -aes-256-cbc -salt -in plaintext.txt -out encrypted.dat -pass pass:YourPassword

Replace plaintext.txt with the name of the file you want to encrypt and YourPassword with a strong password.

Decryption with AES:bashCopy code

openssl enc -d -aes-256-cbc -in encrypted.dat -out decrypted.txt -pass pass:YourPassword

Replace encrypted.dat with the name of the file you want to decrypt and YourPassword with the password you used for encryption.

Generate RSA Keys:bashCopy code

openssl genpkey -algorithm RSA -out private_key.pem -pkeyopt rsa_keygen_bits:2048
openssl rsa -pubout -in private_key.pem -out public_key.pem

This creates a 2048-bit private key (private_key.pem) and a corresponding public key (public_key.pem).

Encryption with RSA:bashCopy code

openssl rsautl -encrypt -inkey public_key.pem -pubin -in plaintext.txt -out encrypted.dat

Replace plaintext.txt with the name of the file you want to encrypt.

Decryption with RSA:bashCopy code

openssl rsautl -decrypt -inkey private_key.pem -in encrypted.dat -out decrypted.txt

Replace encrypted.dat with the name of the file you want to decrypt.

Note: RSA encryption using rsautl is not intended for large amounts of data. It is usually used to encrypt data that is smaller than the RSA key size. For larger data, it is common to encrypt the data using AES and then encrypt the AES key using RSA.

Always ensure that private keys are kept secure and are not transmitted or exposed to untrusted parties. These commands provide a basic introduction to using OpenSSL for encryption and decryption. The actual implementation in a production environment would require a more robust setup, including proper key management and storage practices.

Disclaimer:
While the author of this document possesses knowledge on the topic, they cannot be held responsible for any inaccuracies or omissions contained herein. This material is created strictly for educational purposes. The author has undertaken diligent research before crafting this content; however, it is always possible that certain nuances or details might have been inadvertently overlooked. The technical information presented is accurate as of the time this article was written, but it is important to note that details may evolve or change over time.
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