What Is a Digital Signature?
Digital Signature is a process that guarantees that the contents of a message have not been altered in transit.
When you, the server, digitally sign a document, you add a one-way hash (encryption) of the message content using your public and private key pair.
Your client can still read it, but the process creates a "signature" that only the server's public key can decrypt. The client, using the server's public key, can then validate the sender as well as the integrity of message contents.
Whether it's
- an email
- an online order
- or a watermarked photograph on eBay
How does a Digital Signature Work?
The digital signature can be considered as a numerical value that is represented as a sequence of characters. The creation of a digital signature is a complex mathematical process that can only be created by a computer. Consider a scenario where Alice has to digitally sign a file or an email and send it to Bob.- Alice selects the file to be digitally signed or clicks on 'sign' in her email application
- The hash value of the file content or the message is calculated by Alice's computer
- This hash value is encrypted with Alice's Signing Key (which is a Private Key) to create the Digital Signature.
- Now, the original file or email message along with its Digital Signature are sent to Bob.
- After Bob receives the signed message, the associated application (such as email application) identifies that the message has been signed. Bob's computer then proceeds to:
- Decrypt the Digital Signature using Alice's Public Key
- Calculate the hash of the original message
- Compare the (a) hash it has computed from the received message with the (b) decrypted hash received with Alice's message.
- Any difference in the hash values would reveal tampering of the message.
Class 2 Digital Signature Certificate
As e-filing is made compulsory in ROC (as per MCA 21) / Income Tax / Service Tax / VAT, every director or signing authority needs to have their Digital Signature Certificate. Its now mandatory to obtain Class-2 or Class-2 with PAN Digital Signature Certificate for any person who is required to sign manual documents and returns filed with ROC (as per MCA 21) / Income Tax / Service Tax / VAT . Also an Individual is required to obtain Class-2 DSC with PAN for e-filing his return with Income Tax, India. Thus, Digital Signature Certificate to be obtained by:- Individuals
- Auditors
- Directors
- Company Secretary - in practice or on job.
- Other Authorized Signatories.
- Bank Officials.