Question

"Asymmetric Crypto System" under Information Technology Act means a system of a secure key pair consisting of a private key for creating a digital signature and

• A. an individual key to verify the digital signature
• B. a lock to verify the digital signature
• C. a public key to verify the digital signature
• D. a Government key to verify the digital signature

Hint:

Remember the basic principle of digital signatures under the IT Act: \textbf{Private Key Signs, Public Key Verifies}. This simple rule will help you answer any question on the mechanics of asymmetric crypto systems.

Answer 1

The Correct Option is C

Think of an asymmetric crypto system as a two-key lock and key arrangement, one key stays with the owner and the other is shared with everyone else.

1. an individual key to verify the digital signature: this is not a defined term, asymmetric cryptography works with exactly two named keys, private and public, not an unspecified "individual" key.
2. a lock to verify the digital signature: a lock is not part of how digital signatures are verified, verification is done mathematically using a key, not a physical or virtual lock.
3. a public key to verify the digital signature: this matches the actual mechanism, the signer's private key creates the signature, and the matching public key, which is openly distributed, is used by anyone to check that the signature is authentic.
4. a Government key to verify the digital signature: no such key exists in this framework, verification relies on the signer's own public key, not a key issued by any government authority.

The correct answer is a public key to verify the digital signature.

Answer 2

Since this phrase completes a specific legal definition, it helps to first rule out the options that describe things which do not exist in cryptography, before confirming the correct one on technical grounds.

1. an individual key to verify the digital signature: cryptographic systems do not refer to any key as an "individual key", this phrase does not correspond to any component of a signature scheme.
2. a lock to verify the digital signature: digital signatures are verified using cryptographic keys and algorithms, not a "lock", which is not a term used anywhere in this area of law or technology.
3. a Government key to verify the digital signature: there is no provision for a centrally issued "government key" being used to verify signatures, this option seems designed to sound official but has no basis in the actual mechanism.
4. a public key to verify the digital signature: having eliminated the other three, this is confirmed by how public key cryptography actually works, the private key is used to generate a unique signature, and the corresponding public key, made available to all, allows anyone receiving the signed document to confirm it was signed with that specific private key.

Once the invented options are set aside, the technically accurate completion of the definition is a public key to verify the digital signature.