Digital Signature

Verifiably binds the identity of the signer to the signed data. The signature is created using a private key held exclusively by the signer. Verification succeeds only with the corresponding public key, proving the message could only have come from the holder of that private key. This establishes non-repudiation, preventing the signer from plausibly denying they created the log entry.

Guarantees that the data has not been altered in transit or at rest after signing. The signing process generates a cryptographic hash of the message, which is then encrypted with the private key. Any modification to the original data—even a single bit—produces a completely different hash, causing signature verification to fail immediately.

Provides irrefutable proof of the origin and integrity of the signed data, making it legally and technically impossible for the signer to deny their action. This is achieved because only the signer possesses the private key. Combined with a Trusted Timestamping authority, it creates a legally binding audit trail suitable for e-discovery and regulatory compliance.

The technical workflow that validates a signature without exposing the private key. The verifier uses the signer's widely distributed public key to decrypt the signature, revealing the original hash. The verifier then independently computes the hash of the received message. If the two hashes match, the signature is valid. This process is foundational to Public Key Infrastructure (PKI).

Transforms a standard log into an immutable audit trail. Each log entry is signed individually or as part of a Merkle Tree structure. This creates a tamper-evident seal, allowing a Security Information and Event Management (SIEM) system to automatically detect and alert on any log entry that fails signature verification, indicating potential data corruption or malicious tampering.

The foundational framework for creating, distributing, and revoking digital certificates. PKI establishes a chain of trust by binding public keys to verified identities via a Certificate Authority (CA). In audit logging, PKI ensures the signing key used to create a digital signature belongs to a specific, authenticated system or user, not an impostor.

A one-way mathematical function (like SHA-256) that converts an arbitrary data input into a fixed-size, unique 'digest'. Before signing, a log entry is hashed. The digital signature is then created over this hash, not the raw data. This provides a tamper-evident seal: any change to the log entry, even a single bit, produces a completely different hash, instantly invalidating the signature.

The process of cryptographically binding a verified date and time to a digital document or log entry. A Timestamp Authority (TSA) appends a signed timestamp to the log's hash before it is signed by the local system. This proves that the log data existed at a specific point in time and has not been backdated, a critical requirement for forensic readiness and regulatory compliance.

A technique for amplifying the immutability of an audit trail. Instead of storing entire logs on-chain, a Merkle root representing a batch of signed log entries is embedded into a public blockchain transaction. This provides an immutable, globally verifiable timestamp that proves the logs existed before the transaction's block time, without exposing sensitive log data to a public ledger.