HTTPS (Hypertext Transfer Protocol Secure) is designed to provide secure communication over a computer network by ensuring confidentiality, integrity, and authentication.
However, it does not inherently provide non-repudiation, which is the assurance that a party cannot deny the authenticity of their signature or the sending of a message.
Reasons HTTPS Does Not Provide Non-Repudiation
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Ephemeral Session Keys: HTTPS relies on the TLS (Transport Layer Security) protocol, which uses ephemeral session keys for encrypting data during a session. These session keys are typically generated for the duration of a session and are not tied to a specific user identity in a verifiable way that can be used later to prove the origin of the data.
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Lack of Digital Signatures for Individual Messages: While HTTPS uses certificates to authenticate servers (and sometimes clients), the data transmitted during an HTTPS session is not individually signed with a digital signature that can be independently verified later. This means there is no cryptographic proof linking specific messages to a particular sender in a way that prevents denial.
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Session-Based Authentication: HTTPS sessions are authenticated at the beginning of the connection, but this authentication does not extend to non-repudiation because it does not provide a persistent, verifiable record of individual transactions or messages that can be independently audited.
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Potential for Shared Credentials: In some cases, credentials (such as passwords or even private keys) might be shared among multiple users or systems, making it difficult to attribute actions to a single entity definitively.
Technical Limitations
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Symmetric Encryption: TLS primarily uses symmetric encryption for data transmission after the initial handshake. Symmetric encryption does not provide non-repudiation because both parties share the same secret key, and either could have generated the encrypted data.
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Absence of Audit Trails: HTTPS does not create an immutable audit trail of user actions or transmitted data that can be used to prove the origin and integrity of specific transactions at a later time.
Achieving Non-Repudiation
To achieve non-repudiation, additional mechanisms beyond HTTPS are necessary, such as:
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Digital Signatures: Implementing digital signatures for individual messages or transactions ensures that each piece of data is signed by the sender's private key, providing verifiable proof of origin.
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Public Key Infrastructure (PKI): Utilizing PKI allows for the management of digital certificates and keys, enabling entities to sign data in a way that can be independently verified by others.
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Audit Logs: Maintaining secure, tamper-evident logs of transactions can help provide evidence of actions taken, supporting non-repudiation.
