Key Generator Microservice

A microservice that generates random keys for one-time pad encryption. This service receives file names via ZeroMQ, generates appropriate-length random keys using ASCII printable characters (32-126), and saves them to files.

Installation Requirements

1. Python 3.7 or higher
2. PyZMQ library

Install the required dependencies:

pip install pyzmq

Step-by-Step Installation

1. First, check your Python version:

python --version

2. (Optional but recommended) Create a virtual environment:

python3 -m venv venv
source venv/bin/activate

3. Install the required package:

pip install -r requirements.txt

If you encounter permission errors:

sudo pip install pyzmq

Verify Installation

# Run Python and try:
import zmq
print(zmq.pyzmq_version())

Setup Instructions

1. Clone this repository or download the source files
2. Ensure all files are in your working directory
3. Start the key generator service:

python key_generator_service.py

Communication Contract

How to Request Data

The microservice accepts requests via ZeroMQ on port 5555. Send a string containing the input filename for which you need a key generated.

Example request code:

import zmq

# Setup ZeroMQ context and socket
context = zmq.Context()
socket = context.socket(zmq.REQ)
socket.connect("tcp://localhost:5555")

# Send the filename
input_filename = "message.txt"
socket.send_string(input_filename)

How to Receive Data

The service responds with two parts:

1. Status: "success" or "error"
2. Response: Either the key filename or error message

Example receiving code:

# Receive the response
status, response = socket.recv_multipart()
status = status.decode('utf-8')
response = response.decode('utf-8')

if status == "success":
    key_filename = response
    print(f"Key saved to: {key_filename}")
else:
    error_message = response
    print(f"Error: {error_message}")

UML Sequence Diagram

sequenceDiagram
    participant C as Client Program
    participant K as Key Generator Service
    participant FS as File System
    
    C->>+K: Send filename (ZMQ REQ)
    K->>+FS: Check if file exists
    FS-->>-K: File status
    
    alt File exists
        K->>+FS: Read file length
        FS-->>-K: File length
        K->>K: Generate random key
        K->>+FS: Save key to file
        FS-->>-K: Save confirmation
        K-->>-C: Send success + key filename
    else File not found
        K-->>C: Send error + error message
    end

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Error Handling

The service handles several types of errors:

1. File not found
2. Permission errors when reading/writing files
3. Invalid file formats
4. Network communication errors

Error responses will include descriptive messages to help diagnose issues.

Key Generation Details

• Keys are generated using Python's random.randint()
• Characters are in the ASCII printable range (32-126)
• Key length matches input file length exactly
• Keys are saved in the same directory as the program
• Key filenames are generated as: "key_[original_filename].txt"

File Management

• All generated key files are stored in the same directory as the program
• Files are automatically named based on the input filename
• Existing files with the same name will be overwritten
• UTF-8 encoding is used for all file operations

Usage Example

1. Start the service:

python key_generator_service.py

2. In your client code:

import zmq

def request_key(filename):
    context = zmq.Context()
    socket = context.socket(zmq.REQ)
    socket.connect("tcp://localhost:5555")
    
    socket.send_string(filename)
    status, response = socket.recv_multipart()
    
    status = status.decode('utf-8')
    response = response.decode('utf-8')
    
    return status, response

# Example usage
status, response = request_key("message.txt")
if status == "success":
    print(f"Key generated and saved to: {response}")
else:
    print(f"Error: {response}")

Troubleshooting

Common issues and solutions:

1. "Address already in use" error:

   • Another instance of the service is running
   • Wait a few seconds and try again, or use a different port

2. "Connection refused" error:

   • Service is not running
   • Check if service is started on the correct port

3. "File not found" error:

   • Verify the input file exists
   • Check file path is correct
   • Ensure proper file permissions

Testing

Run the included test program to verify the service is working:

python test_key_generator.py

The test program will:

1. Create a test input file
2. Request a key
3. Display the results