How Does a Digital Signature Certificate (DSC) Work?
A Digital Signature Certificate (DSC) works using Public Key Infrastructure (PKI), cryptographic hashing, and a pair of mathematically related keys known as the Private Key and Public Key. Together, these technologies verify the identity of the signer, protect document integrity, and provide legally recognized electronic signatures under the Information Technology Act, 2000 in India.
Step-by-Step: How a DSC Works
1. Identity Verification
Before issuing a Digital Signature Certificate, the applicant's identity is verified by a Licensed Certifying Authority (CA). Depending on the certificate type and regulatory requirements, verification may include Aadhaar-based verification, PAN validation, organization documents, email and mobile verification, or other approved identity checks.
2. Generation of Key Pair
After successful verification, a unique cryptographic key pair is generated. The Private Key remains securely under the signer's control, while the Public Key becomes part of the Digital Signature Certificate.
3. Document Hashing
When a document is digitally signed, a cryptographic hash (a unique digital fingerprint) of the document is created using secure hashing algorithms such as SHA-256. Even a one-character change creates a completely different hash value.
4. Digital Signing
The generated hash is digitally signed using the signer's Private Key. This signed hash becomes the digital signature attached to the document. The Private Key never leaves the signer's secure environment.
5. Signature Verification
Anyone receiving the document can use the Public Key contained in the Digital Signature Certificate to verify the signature. If the calculated hash matches the signed hash, the document is confirmed as authentic and unaltered.
6. Certificate Validation
The software also verifies whether the Digital Signature Certificate was issued by a trusted Licensed Certifying Authority and whether the certificate is valid, expired, or revoked before accepting the signature.
Why Is a Digital Signature Secure?
- Confirms the identity of the signer.
- Protects documents from unauthorized modification.
- Detects even the smallest change made after signing.
- Uses internationally accepted cryptographic standards.
- Provides authentication.
- Maintains document integrity.
- Supports non-repudiation, meaning the signer cannot later deny signing the document.
- Can be independently verified by anyone with the Public Key.
What Information Does a Digital Signature Certificate Contain?
- Certificate holder's name.
- Certificate serial number.
- Public Key.
- Name of the Licensed Certifying Authority (CA).
- Certificate validity period.
- Digital signature of the issuing CA.
- Certificate policies and identification details.
Did You Know?
A Digital Signature does not simply place an image of your handwritten signature on a document. Instead, it creates a mathematically verifiable cryptographic signature that proves who signed the document and confirms that the document has not been modified after signing.
