How It Works: Sign Documents with Face ID
Egregor lets you sign files using the same security technology that protects your Face ID data and Apple Pay. It creates a digital signature that is legally valid in most countries, including under the eIDAS regulation in the EU and the ESIGN Act in the US.
Step 1: Your iPhone creates a key that never leaves it
- Private key: A secret number generated inside your iPhone's Secure Enclave chip. It is used to create signatures.
- Public key: A non-secret number linked to your private key. Anyone with your public key can verify that a signature was created by your private key.
Step 2: Your file gets a unique fingerprint
To sign a file, Egregor first calculates its SHA-256 hash. This is a 64-character code that acts like a digital fingerprint. If even one pixel in an image or one comma in a document changes, the fingerprint changes completely. We never see your file—only this fingerprint.
Step 3: You sign the fingerprint
When you authorize with Face ID or Touch ID, the Secure Enclave uses your private key to mathematically "sign" the fingerprint. This produces a signature: a block of data that can only be generated by someone who has both the file and your private key.
Step 4: Anyone can verify it
You share the file and the signature. Anyone can use your public key to verify that the signature matches the file's fingerprint. If the file was modified or the signature was created by a different key, verification will fail.
Knowing who really signed: identity verification
By default, Egregor signatures are "self-signed," meaning they prove a specific device signed the file. To link a signature to a legal name, you can verify your identity with a passport or ID card. We then issue a certificate that links your public key to your verified name.
Certificates you can check without us
- Open standards, not secret methods. We use standard ECDSA cryptography (NIST P-256 curve).
- Independent verification. You can download a PDF certificate for any signature. This certificate contains the public key and all the math needed to verify the signature using standard tools, even if our app or servers disappear.
Why it's trustworthy
- Hardware security. The signing key is protected by the same hardware that stores your biometrics.
- Biometric enforcement. iOS ensures that a signature is only created after a successful Face ID or Touch ID check.
- No central database of keys. We don't store your private key, so we can't be hacked or forced to sign on your behalf.
What Egregor does not do
- No file storage. We don't keep copies of your documents.
- No tracking. We don't track who you are signing with or what is inside your files.
- No vendor lock-in. Your signatures are based on open math, not a proprietary format.
Building software that needs to check signatures? See the Developers page.