At HelloSign, each of your documents is stored behind a firewall and authenticated against the sender’s session every time a request for that document is made. All communications use SSL (Secure Sockets Layer) encryption and all data is stored in a SOC 1 Type II, SOC 2 Type II, and ISO 27001 certified data center. Your documents are stored and encrypted at rest using AES 256-bit encryption.
Here is a bit more about how your data is encrypted:
All HelloWorks documents are encrypted at rest using AES 256-bit encryption
For any document in transit to be signed, all communications are encrypted using SSL/TLS