DKIM Recipient Binding for Replay-Resistant Email Authentication
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Domain Keys Identified Mail (DKIM) is vulnerable to replay attacks and disrupts mailing and forwarding lists, failing to provide adequate protection for message authenticity and privacy.
Innovation Solution
A message protocol that enhances DKIM by explicitly declaring all recipients, including hidden recipients, and employs challenge requests to verify sender authenticity, while allowing header and body modifications with dual signatures to maintain authenticity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DKIM digitally signs messages using public-key cryptography, then message authenticity is protected, but the system becomes vulnerable to replay attacks
Solution Approach 1:
The patent applies preliminary action by including recipient information in the DKIM signature during the initial message signing process. This pre-binds the message to its intended recipients, so that any subsequent replay attempt to a different recipient will fail verification. The signature is created in advance with recipient data embedded, preventing later misuse of the signature for replay attacks.
2Reliability
If DKIM verifies message authenticity through cryptographic signatures, then message integrity is ensured, but mailing and forwarding lists are disrupted
Solution Approach 1:
The patent performs preliminary action by embedding recipient list information in the signature before mailing or forwarding operations occur. This allows subsequent mailing list expansions or forwarding operations to be performed without breaking the signature, as the signature already anticipates multiple recipients. The pre-included recipient data enables flexible list management while maintaining integrity verification.
3Ease of operation
If DKIM signs messages without including recipient information, then signature verification is simple, but privacy is compromised and replay attacks are enabled
Solution Approach 1:
The patent applies segmentation by dividing the recipient information into multiple parts or representations that can be included in the signature in a structured manner. This segmentation allows the signature to contain necessary recipient data for privacy protection and replay prevention while maintaining a systematic verification process that doesn't overly complicate the operation. The segmented approach organizes recipient data efficiently within the signature structure.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A method (700) includes obtaining, at a message server (160), a message (152) for a user (12) of a message service hosted by the message server. The message includes a header (310) and the header includes a digital signature (330) signed by an author of the message and a list of one or more recipients (312) of the message. The method includes determining whether the digital signature by the author is valid and determining, using the list of one or more recipients, whether the user is a declared recipient of the message. When the digital signature by the author is valid and the user is the declared recipient of the message, the method includes delivering the message to a user device of the user. When the digital signature by the author is valid and the user is not the declared recipient of the message, the method includes alerting the user.