To be honest, after playing with it a bit, I see that there is something more, but I have no idea what it is yet - hopefully none of our private keys

I just stream the serialized data of the CWalletTx object to CDataStream type of object and then base58 it - and that's the content of the file.

But I noticed that usually the file is bigger than you would expect from the actual format of the tx block - it doesn't end at the lock_time but is longer...

I'm trying to figure out what this extra data is.

For example the raw data is something like this (hex dump):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... while I would expect the transaction data to only be the blue part. So what is this red stuff at the end? I have no idea, but I'm going to find it out.