Follow these steps to create and verify digital signatures using RSA with SHA-1 hashing:

📝 Step 1: Enter Plaintext and Generate Hash

The first step involves entering your message and creating its cryptographic hash:

• Enter your message in the Plaintext (string) field (default: "test")
• Click the "Generate SHA-1 Hash" button to compute the SHA-1 hash
• The hash will automatically appear in the Hash output (hex) field below
• This hash represents a fixed-size fingerprint of your original message

The light blue section clearly indicates this is the input and hashing phase.

🔑 Step 2: Input Hash to RSA

The second step prepares the hash for RSA signature creation:

• The system automatically copies the generated hash to the Input to RSA (hex) field
• If needed, you can manually copy the hash value from Step 1
• Verify that both hash fields contain identical values
• Click "Apply RSA Signature" to create the digital signature using RSA encryption

The light orange section distinguishes this RSA processing phase.

✅ Step 3: View Digital Signature Results

The third step displays your digital signature in multiple formats:

• Digital Signature (hex): The signature in hexadecimal format for technical analysis
• Digital Signature (base64): The same signature in base64 encoding for easy transmission
• Status: Shows success confirmation with processing details or error messages
• Digital Signature Summary: A comprehensive table showing all parameters and results

The light green section clearly indicates successful completion and results.

⚙️ Step 4: Select RSA Public Key

The fourth step involves configuring the RSA cryptographic parameters:

• Important: You must select a key size before applying the RSA signature in Step 2
• Public exponent: Shows the current exponent value (typically 3 or 65537)
• Modulus: Displays the RSA modulus in hexadecimal format
• Key Size Selection: Choose from four available options:
  • Load 1024-bit Key (e=F4): Standard 1024-bit key with exponent 65537 (recommended)
  • Load 1024-bit Key (e=3): 1024-bit key with small exponent 3 (faster)
  • Load 512-bit Key (e=F4): Smaller 512-bit key with exponent 65537 (educational use)
  • Load 512-bit Key (e=3): 512-bit key with small exponent 3 (fastest, least secure)

The light purple section emphasizes the importance of key configuration.

🔍 Understanding the Digital Signature Process

Cryptographic Workflow:

1. Message Hashing: SHA-1 creates a 160-bit digest of any input message
2. Private Key Signing: RSA encrypts the hash with the private key to create the signature
3. Public Key Verification: Others can verify authenticity using the corresponding public key
4. Integrity Assurance: Any message modification will result in signature verification failure

Security Properties:

• Authentication: Confirms the signer's identity
• Integrity: Detects any message tampering
• Non-repudiation: Prevents denial of signature creation

🔧 Troubleshooting Common Issues

Issue	Solution
"Invalid RSA public key"	Select a key size in Step 4 before applying RSA signature
"Hash and RSA input mismatch"	Ensure both hash fields contain identical values
"No hash generated"	Click the "Generate SHA-1 Hash" button in Step 1 first
Empty signature results	Verify all previous steps are completed in order
Mobile display issues	Use landscape orientation or access from desktop for best experience