What is a digital signature ? What does its authentication mean ? Give various salient built-in features…

Question

What is a digital signature ? What does its authentication mean ? Give various salient built-in features of a digital signature.

Ghissu Editorial · Accepted Answer

A digital signature is a code made with the signer's private key and a hash function, and authentication means confirming through the public key that a record came from the claimed signer unaltered. Its built-in features are integrity, non-repudiation, document-specificity, revocability and legal validity under the IT Act, 2000.

**Introduction**

The digital signature is the electronic equivalent of a handwritten signature and seal, and Section 3 of the Information Technology Act, 2000 recognises it for authenticating electronic records such as GST returns and MCA21 filings.

**Digital Signature and Its Authentication**

1. **Meaning**: It is a mathematical code created with the signer's private key under an asymmetric cryptosystem and a hash function, backed by a Digital Signature Certificate from a licensed Certifying Authority.
2. **What authentication means**: The recipient can confirm that the record came from the claimed signer and was not altered afterwards, since only the matching public key opens the signature.

SKETCH: flow | Signing and Verifying
- Document hashed
- Hash locked by private key
- Signature sent with document
- Public key unlocks hash
- Hashes match: authentic

3. **Chain of trust**: The Controller of Certifying Authorities under Section 17 of the IT Act licenses the Certifying Authorities, as in the Aadhaar-based eSign service of 2015.

**Salient Built-in Features**

1. **Integrity**: A change of a single character alters the hash, exposing tampering at once.
2. **Non-repudiation**: Only the signer holds the private key, so the signer cannot deny signing, and Section 5 of the IT Act gives it the legal standing of a handwritten signature.
3. **Document-specific**: Each signature is computed from one document and cannot be pasted onto another.
4. **Validity and revocation**: The certificate expires and can be revoked if the key is compromised, and a timestamp fixes the signing time.
5. **Secure key storage**: The private key sits on a PIN-protected cryptographic token.

**Conclusion**

By proving who signed, what was signed and that nothing changed, the digital signature underpins paperless governance under Digital India, provided the private key stays secret.

What is a digital signature ? What does its authentication mean ? Give various salient built-in features of a digital signature.

Model answer

Practise this question

IT5 questions

Ghissu