DX(G) Collections file

Hi

I have been trying to manually create collection files. On the internet I found that they should be sha1 checksums.

I created test collections on my Kindle and got this in collections file :
{"mobi@en-US":{"items":["*bb8e4393924c8a3a6622b339485b0d1f89c6dcbc",
"#bcc85a69-17b2-47d6-a084-d137db9cf50c^EBOK",
"#de2f8b3e-37ac-4229-a3be-4d55e42b9d83^EBOK",
"*98fa5c60d5acde87b9244ca4c0a409e7be58958a",
"#6187d2ea-4971-41fb-9896-a70cf0b418ae^EBOK",
"#61e1de5a-1182-4b54-b703-871daaa978fa^EBOK",
"#70897660-9e7f-44cc-bcaf-95a883b52f17^EBOK"],"lastAccess":1370716940938}}

And I have no idea how those hashes are created...

Anyone knows?