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You are handing over the keys to your entire digital life just to send a single PDF. And it’s time to stop.
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What our first week actually showed—and what it did not prove.
This is why we built SEYFR: you deserve to stay in charge of your most important files.
The Bank Card and Bank Account Analogy
Letting Child Components Talk to Parents
File transfer software handles data people care about, so trust should come from specific, testable boundaries—not slogans.
A 2021 Trend Micro report described serious vulnerabilities in SHAREit. That history is worth learning from, but it does not prove that every peer-to-peer product is unsafe, and it does not make SEYFR automatically secure. The useful question is: what does SEYFR actually do?
SEYFR works with the files or folders you select through the controls provided by the operating system. The exact permission model differs across Android, iOS, macOS, Windows and Linux. We should not claim that the app is “mathematically incapable” of accessing anything else; platform permissions and the released implementation are the evidence that matters.
Received data is written into the destination chosen or allowed by the receiving platform. SEYFR’s implementation validates destination paths so a name such as ../../other-file cannot simply escape the intended receive directory. That is a concrete protection against directory-traversal writes—not a promise that no security bug can ever exist.
The QR code does not contain the file.
It contains the information needed to find the sender and a 32-byte BLAKE3 content hash. A content hash is a cryptographic fingerprint: it identifies the expected bytes without revealing or storing those bytes inside the hash.
Iroh’s blobs protocol verifies the transferred content in small chunks and checks it against that fingerprint. If the received bytes do not match, verification fails.
SEYFR uses Iroh networking. Iroh attempts a direct encrypted connection between the devices. Some routers, firewalls and mobile networks prevent that route, so Iroh can fall back to relay infrastructure.
The relay forwards end-to-end encrypted traffic and cannot read the file contents. This is why “always direct,” “no server,” and “never touches infrastructure” would be inaccurate descriptions.
Direct connections can expose each peer’s IP address to the other peer. Relay operators can observe connection metadata needed to operate the service, even though they cannot read the encrypted file contents.
SEYFR is designed to:
No responsible product should promise “absolute control,” “100% security,” or immunity from every future vulnerability. Our promise is simpler: explain the design precisely, correct mistakes publicly and keep improving the implementation.
Read the SEYFR architecture and get the app
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