Show HN: SignatureAPI – Electronic Signature API

Our API lets you create and track e-signature transactions ("envelopes"), while the actual signing (the "ceremony") happens in a user interface we provide. You can customize, localize, and brand this UI, embed it into your web or mobile app, or send a link to your signers to sign.

We cryptographically sign (or seal) the document to meet the integrity and tamper-proof requirements of most regulations.

Here on HN, we know you can seal the document by signing the hash with a private key and a self-signed certificate. Technically, the e-signatures inside are OK, the seal is cryptographically valid, and the document is tamper-proof, but good luck explaining that to a layperson (like a judge) when they open the document in Acrobat and get a scary red alert saying the signatures are invalid.

At SignatureAPI, we seal the document with a certificate that has a trust chain ending in a root certificate in the Adobe Approved Trust List. This gets you a reassuring green checkmark and a message "the signatures are valid" when the document is opened in Acrobat or Acrobat Reader.

You can check out an example here: https://signatureapi.com/docs/resources/deliverables/audit-l...

Not many e-signature providers offer this green checkmark. Docusign, Dropbox, and Adobe do, but most others don't even cryptographically seal the document—which should raise red flags about whether they really know what they're doing legally.