"Hash" values in Solution manifests

I am currently working to script the upgrade process for eSpaces because we use Linux + Jboss and Platform Server cannot do this. When the script is done, I want to put the files back into a Solution so we can 1CP that single file.

The Manifest.xml file has a "Hash" value in it (sample attached). Does anyone know what hashing algorithm it uses?

I noticed a few things:

* The Hash values for Extensions end in "==" (base64?)and are 24 characters long.
* The Hash values for eSpaces do NOT end in "==" and are 22 characters long.
* I tried to base64 decode the hash values and got junk back.
* My guess is that SHA-1 or MD5 is involved somewhere in this.