What is the signature format outputted by the functions signData and signHash?

The functions signData and signHash perform a digital signature algorithm using the private key of one of the user's certificates. Therefore, their output is the raw output of the algorithm, encoded in Base64. In the most common case of an RSA algorithm using a 2048-bit key, the output is 256 bytes long (344 characters in Base64).

This question normally arises from the confusion between a digital signature, such as CMS/CAdES, XmlDSig/XAdES and PAdES, and a digital signature algorithm, such as RSA. Usually, digital signature algorithms are a small part of the implementation of digital signatures. The signData and signHash perform only the algorithm, not the entire digital signature.

Please see the FAQ How can I perform a digital signature with Web PKI? for information on how to use Web PKI to perform digital signatures.