I have been working with Axis 1.x, WSS4J for sometime. There is a propietary intermediary that we are using that just acts like a kind of proxy between the consumer and provider. This intermediary will not modify the soap message when it passes the soap message from the consumer to the provider.
I usually sign the body and try to verify the signature and occassionaly I face an exceptions like "digest value mismatch" while trying to validate the signature. What I feel is after the soap messages with signature reach from the consumr to the provider, on the provider end somehow the body gets modified with some not so eye visible newline characters, spaces etc. that breaks the signature verification. When WSS4J calculates the digest on the body and compares this digest value with the digest value that is already present in the digest value element of the SignedInfo element then if they both do not match then I get "digest value mismatch" error from WSS4J. All this stuff may happen even with the signature value.
I tried these settings on both client side and provider side with Axis 1.2, Axis 1.2.1, Axis 1.3, Axis 1.4, WSS4J 1.5 but these settings did not solve the problem even though I dont really what these settings do.
Now my question is do we have any workaround may be at the axis level or wss4j for fixing this problem because I dont have any control on the intermediary if by any chance it is modifying the soap message when it passses the message to the provider and I am pretty sure that in our case it WILL not modify the soap message.
Canonical XML finds its application in this scenario. The signing authority will digest and sign the canonical form of the document instead of the original form. Similarly, at the time of verification, the canonical form will be verified instead of the original XML. Thus all logically equivalent versions of the signed XML document will result in successful verification (validation) of XML digital signatures.
Read more about Canonicalizing Before Signing and Verifying here.
And here's one good article on the xml signature validation.