PKCS#7Viewer ... Finally, a graphical tool for inspecting ASN.1 parse trees aka Mac App Store Receipts and codesign/SSL certificates encoded in the ASN.1 DER/BER format. Use alone or in conjunction with Tighten Pro code generator.
Aimed primarily at Cocoa developers writing and testing code for In-App Purchase Receipt validation, PKCS#7Viewer can open and inspect almost any PKCS ASN.1 DER/BER encoded container.
Some examples of files in this format:
Easily inspect the basic fields included with every MASReceipt or drill down into details of individual In-App Purchase items. The parse tree hierarchy shows exactly what's been included in the receipt, including undocumented but nevertheless useful receipt fields.