The short answer is no. Authenticated Received Chain (ARC) is a powerful email authentication protocol, but it does not provide end-to-end encryption. These two technologies address entirely different aspects of email security, and it's a common point of confusion.
ARC is designed to solve a problem with authentication, specifically how DMARC, SPF, and DKIM results can break when an email is forwarded. End-to-end encryption, on the other hand, is focused on ensuring the content of a message remains private and unreadable to anyone except the sender and the intended recipient.
What ARC actually does
ARC's primary role is to preserve email authentication results as a message travels from its origin to the final mailbox. When an email is sent directly, authentication is straightforward. The recipient's server checks the sender's SPF and DKIM records, and based on the sender's DMARC policy, decides whether to accept the message.
However, this process breaks with intermediaries like mailing lists or forwarding services. These services often modify the email (like adding a footer), which breaks the DKIM signature. They also send the email from their own servers, which breaks the SPF alignment. ARC was created to fix this.
- An intermediary (like a mailing list server) receives an email.
- It validates the original DMARC, SPF, and DKIM results.
- Before forwarding the email, it attaches a new ARC-Authentication-Results header with the original validation results.
- It then signs these results with its own DKIM-like signature in an ARC-Seal header.
- When the final recipient's server gets the email, it may see that SPF and DKIM fail. However, it can then check the trusted ARC seal, see the original 'pass' results, and deliver the legitimate email.
The goal of end-to-end encryption
End-to-end encryption (E2EE) has a completely different function: confidentiality. Its only goal is to ensure that message content is protected from being read by anyone other than the sender and the recipient. When a message is end-to-end encrypted, it is converted into unreadable ciphertext on the sender's device and can only be decrypted on the recipient's device.
Even the email servers and providers that handle the message in transit cannot decipher its content. This is a much stronger form of privacy than the standard TLS encryption used by mail servers, which only protects data between servers but leaves the message readable on the servers themselves.
Authentication vs. confidentiality
So, we can see the clear distinction. ARC is concerned with proving an email's origin and journey are legitimate (authentication). It actually adds readable headers for servers to inspect. E2EE is concerned with making an email's content unreadable to everyone except the final participants (confidentiality).
In short, ARC is a crucial tool for email deliverability, ensuring your authenticated messages reach their destination through complex routing paths. But for true message privacy, you need to use separate solutions like PGP or email services that have E2EE built-in. ARC verifies the envelope, while E2EE protects the letter inside.
Does ARC prevent email spoofing?
What ARC header contains a cryptographically signed copy of the message's state?
Does ARC add a new digital signature to the email?
Does ARC preserve original authentication results?
Does ARC prevent message alteration after signing?
Does ARC require a private key for signing?
