Digital Signatures and Non-Repudiation in CASP+

Digital signatures utilize asymmetric cryptography and hashing to prove the origin of a message (authentication), guarantee it hasn't been altered (integrity), and prevent the sender from denying they sent it (non-repudiation).

How Digital Signatures Work

To create a digital signature, the sender hashes the message and then encrypts that hash with their own private key.

The receiver decrypts the signature using the sender's public key to reveal the hash, and then independently hashes the message. If the hashes match, the signature is valid.

Achieving Non-Repudiation

Non-repudiation ensures that a party to a contract or communication cannot deny the authenticity of their signature on a document or the sending of a message.

Because the digital signature is tied to a specific individual's private key, and only they possess that key, they cannot claim someone else sent the message.

Code Signing for Software Integrity

Digital signatures are critical for code signing, which proves to users that a software patch or executable comes from a trusted developer and hasn't been tampered with.

Operating systems and application platforms heavily rely on code signing to block malicious software from executing. Reviewing code signing scenarios with Cert Sensei is an excellent way to prepare for exam simulations.

Legal and Regulatory Importance

In many jurisdictions, digital signatures hold the same legal weight as a physical signature on a document.

Security practitioners must ensure that the underlying PKI and key protection mechanisms are robust enough to withstand legal scrutiny and compliance audits.

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