When X509_DSS_SIGNATURE is used for the lpszStructType with CryptEncodeObject, CryptEncodeObjectEx, CryptDecodeObject, or CryptDecodeObjectEx the following details apply.
N/A
pvStructInfo points to an array of 40 BYTEs. The bytes are ordered as output by the DSS CSP's CryptSignHash() where the lower 20 bytes are the R value, and the higher 20 bytes are the S value. The R and S values are treated as unsigned integers and encoded as a sequence of them.
See Generating DSS Signatures.