BMP File Encryption - Python Programming Exercise

In this exercise, you will develop a Python program to encrypt or decrypt a BMP image file by swapping the "BM" signature in the first two bytes with "MB" and vice versa. This exercise is perfect for practicing file handling, byte manipulation, and encryption techniques in Python. By implementing this program, you will gain hands-on experience in handling file operations, byte manipulation, and encryption techniques in Python. This exercise not only reinforces your understanding of file handling but also helps you develop efficient coding practices for managing user interactions.

 Category

Managing Files

 Exercise

BMP File Encryption

 Objective

Develop a Python program to encrypt or decrypt a BMP image file by swapping the "BM" signature in the first two bytes with "MB" and vice versa.

Utilize the advanced FileStream constructor to allow reading and writing at the same time.

 Example Python Exercise

 Copy Python Code 
# Python program to encrypt or decrypt a BMP file by swapping the "BM" signature

def encrypt_decrypt_bmp(filename):
    try:
        # Open the BMP file in binary read and write mode
        with open(filename, 'r+b') as file:
            # Read the first two bytes (the signature)
            signature = file.read(2)
            
            # Check if the signature is "BM"
            if signature == b'BM':
                print("Encrypting: Swapping 'BM' to 'MB'...")
                # Move the file pointer back to the start
                file.seek(0)
                # Write "MB" to replace "BM"
                file.write(b'MB')
            elif signature == b'MB':
                print("Decrypting: Swapping 'MB' to 'BM'...")
                # Move the file pointer back to the start
                file.seek(0)
                # Write "BM" to replace "MB"
                file.write(b'BM')
            else:
                print(f"Error: The file '{filename}' does not have a valid BMP signature.")
                
    except FileNotFoundError:
        print(f"Error: The file '{filename}' does not exist.")
    except Exception as e:
        print(f"Error: {str(e)}")

# Example usage
encrypt_decrypt_bmp("example.bmp")

 Output

Encrypting: Swapping 'BM' to 'MB'...

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