Email Sender Verification via Attachment Encryption
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Solution Overview
Problem
Phishing attacks exploit human trust by spoofing email sender information, making it difficult for users to distinguish authentic from inauthentic emails, even for sophisticated users, as existing methods rely heavily on user education and awareness.
Innovation Solution
An email server decrypts attachments using a key associated with the sending device and inserts a device identifier into the email message as a header, encrypting all attachments with a key linked to the device identifier, disarming potentially harmful emails by adding a header and stripping attachments if decryption fails or if the identifier is missing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If user education is used to prevent phishing attacks, then users can be made more aware of security risks, but sophisticated users can still make mistakes and the prevention is not automatic
Solution Approach 1:
The email system performs automatic sender verification through encryption validation without requiring user intervention. The receiving email server automatically decrypts attachments using the sender's public key and validates the decryption result, providing self-service security verification that eliminates reliance on user awareness while achieving automatic identification of phishing attempts
Solution Approach 2:
Encryption keys act as an intermediary mechanism between sender and receiver to verify authenticity. The sender's public key serves as a mediator that enables the receiving server to automatically validate the sender's identity through decryption operations, transforming a manual verification process into an automated cryptographic validation system
2Extent of automation
If encryption is applied to all attachments, then sender authenticity can be verified automatically, but the system complexity increases with key management requirements
Solution Approach 1:
The public key encryption system serves multiple functions simultaneously: it encrypts attachments for confidentiality, enables automatic sender verification through decryption validation, and provides authentication without requiring separate key management infrastructure. This multi-functionality reduces overall system complexity despite the cryptographic operations involved
Solution Approach 2:
The system uses the sender's existing public key (which is already distributed and available) rather than requiring new key pairs to be generated and managed for each verification operation. The public key acts as a reusable copy that simplifies the verification process while maintaining security
3Object-affected harmful factors
If attachments are stripped from potentially harmful emails, then network security is enhanced, but legitimate encrypted attachments may be removed
Solution Approach 1:
The receiving email server performs a feedback loop by attempting to decrypt attachments using the sender's public key and evaluating the decryption result. If decryption succeeds, the attachment is considered legitimate and is delivered; if decryption fails or is not attempted, the attachment is identified as potentially harmful and is stripped. This feedback mechanism ensures accurate distinction between legitimate and malicious attachments
Data Source
AI summary
An e-mail server decrypts attachments of an e-mail message with a key associated with a sending device such that failure of the decryption indicates the e-mail message can be harmful. The sending device inserts its device identifier into the e-mail message as a header and uses an encryption key associated with the device identifier and a digital fingerprint of the sending device to encrypt all attachments of the e-mail message. The delivering e-mail server processes the e-mail message. If the e-mail message contains no identifier, if no key is associated with the parsed identifier, or if attempted encryption fails, the e-mail server determines that the e-mail message is potentially harmful and disarms the e-mail message.