What is required to verify the authenticity of a digitally signed document?

To verify the authenticity of a digitally signed document, a public key is used. When a document is digitally signed, the signer creates a unique signature using their private key. This signature is an encrypted hash of the document, ensuring both its integrity and authenticity. To verify this signature, the recipient utilizes the corresponding public key, which can decrypt the signature.

Using the public key allows the recipient to confirm that the signature was created using the associated private key, thereby validating that the document has not been altered and that it truly comes from the purported signer. This cryptographic process is foundational to public key infrastructure (PKI) and underpins electronic transactions and communications today, establishing trust without requiring the sender's private key to be shared.

This process ensures that anyone with access to the public key can verify the document's origin and integrity, but cannot replicate the signature, maintaining the security of the private key.