Digital Signature Algorithm

Project 1 demonstrates generating a DSA (Digital Signature Algorithm) key pair using the cryptography library, where a 2048-bit private key is created and a corresponding public key is derived. The private key is essential for securely signing digital messages, and the public key allows others to verify these signatures. Both keys are serialized into PEM format, making them suitable for storage or transmission. The private key is serialized without encryption (though encryption is optional), while the public key is also serialized for easy sharing and use in cryptographic operations.

Project 2 is a DSA (Digital Signature Algorithm) Key Generator application built with Python's tkinter for the GUI and the cryptography library for key generation. It provides an intuitive interface to generate, view, and save 2048-bit DSA key pairs, essential for secure digital signatures. The GUI features two tabs: "Generate Keys" for creating and serializing keys into PEM format, and "View Keys" for displaying them. Users can save the keys as .pem files with ease, supported by robust error handling and success notifications, making the application accessible and practical for secure communication needs.

Project 3 demonstrates the process of signing and verifying a message using the Digital Signature Algorithm (DSA) in Python, while ensuring the signature is UTF-8 safe by encoding it in Base64. It begins by generating a DSA private and public key pair with a key size of 2048 bits. A message (in bytes) is then created, which is the data to be signed. The private key is used to generate a digital signature for the message using the SHA-256 hashing algorithm, ensuring the integrity and authenticity of the message. The generated signature, which is binary data, is encoded into Base64 format to make it text-safe and suitable for UTF-8 encoding.

To verify the signature, the Base64-encoded signature is first decoded back into its original binary form. The public key is then used to verify the authenticity of the signature by comparing it to the message. If the verification is successful, the message "Signature is valid." is printed; otherwise, an InvalidSignature exception is raised, and the message "Signature is invalid." is displayed. This approach ensures that the digital signature can be safely transmitted or stored as text without data corruption, while still preserving its security properties.

Project 4 is a Tkinter-based GUI application for Digital Signature Algorithm (DSA) operations, offering an intuitive interface for generating DSA keys, signing messages, and verifying signatures. It has two main tabs: one for generating and displaying DSA key pairs in PEM format, and another for signing and verifying messages. Users can input a message, sign it with the private key, and view the Base64-encoded signature, or verify a signature against the original message using the public key. The application handles errors gracefully, providing feedback on operations, making it a practical tool for cryptographic tasks.

Project 5 and 6 provides a complete implementation for generating, signing, and verifying files using the Digital Signature Algorithm (DSA). It includes functions for creating DSA key pairs, signing file contents, and verifying signatures. The generate_and_save_keys() function generates a private and public key, serializes them to PEM format, and saves them to files. The sign_file() function uses the private key to sign the SHA-256 hash of a file's content, saving the signature in Base64 format. The verify_file_signature() function then verifies this signature using the public key, ensuring the file's authenticity and integrity.