SYNCOPE-1198 - Adding docs

src/main/asciidoc/reference-guide/workingwithapachesyncope/systemadministration/keystore.adoc

@@ -120,4 +120,21 @@ keystore.type=jks
 keystore.storepass=astorepass
 keystore.keypass=akyepass
 sp.cert.alias=saml2sp
+signature.algorithm=RSA_SHA1
 ....
+
+The `signature.algorithm` configuration parameter is the signature algorithm
+that is used with the key extracted from the keystore referenced in the
+parameters. The value for this parameter must match one of the values in the
+table below, each of which correspond to a shorthand for an associated
+algorithm as defined for use in the XML Signature specification. If 
+`signature.algorithm` is not specified, then either RSA_SHA1, EC_SHA1 or
+DSA_SHA1 is used depending on the type of key that is stored in the keystore.
+
+----
+RSA_SHA1, RSA_SHA224, RSA_SHA256, RSA_SHA384, RSA_SHA512,
+RSA_SHA1_MGF1, RSA_SHA224_MGF1, RSA_SHA256_MGF1, RSA_SHA384_MGF1, RSA_SHA512_MGF1,
+EC_SHA1, EC_SHA224, EC_SHA256, EC_SHA384, EC_SHA512,
+HMAC_SHA1, HMAC_SHA224, HMAC_SHA256, HMAC_SHA384, HMAC_SHA512,
+DSA_SHA1
+----