| How To's / Compute a hash value from a 4GL string | |
This document explains how to compute a hash value of a 4GL string using the security.Digest API.
Signing a XML document is nothing more than computing a hash over a fragment of XML. If you set the string you need to hash in an XML node, and use the correct XPath expression, the security.Digest API will do it for you.
Some special characters are escaped in XML. If you use one of them, the computed hash value will be wrong because the result is actually computed over the escaped string. The special characters to be aware of are: ", ', &, < and >.