Digital Signature

A digital signature is a cryptographic mechanism confirming that a specific person signed a digital document and the document hasn’t been altered since signing. It’s legal equivalent of physical signature, but with greater security. Instead of simple electronic signature (just “name”), digital signature uses complex mathematics to guarantee authenticity.

How does it work? A person uses their private key (secret password only they know) to “sign” document. This process creates a numerical code (hash) unique to that document. If someone later tries changing one character, hash changes, showing document is altered. The recipient can use public key (available to everyone) to verify the signature is authentic.

Practical example: Startup sends contract with lawyer via email. Instead of meeting physically and signing paper, both use digital signature. Startup signs contract with private key, lawyer verifies with public key. Contract is legally valid without physical meeting.

Digital signature advantages: (1) Legal validity—same value as physical signature in most jurisdictions; (2) Speed—signing happens in seconds; (3) Unforgeable—impossible to forge because mathematically impossible to create same hash with different document; (4) Auditability—everyone can see who signed what and when; (5) Digitalization—no need for papers.

For startups: Digital signature is mandatory if you sign anything—contracts, NDAs, financial documents. Use trusted services like DocuSign, HelloSign, or similar.