Reading monero's site I got the impression that it would be impossible to know who Bob and Alice are looking at the block chain alone. However, if you had Bob's

Reading monero's site I got the impression that it would be impossible to know who Bob and Alice are looking at the block chain alone. However, if you had Bob's secret keys you'd know all the money he received and, if you have the sender's private keys, you'd be able to know them too. That's certainly better than bitcoin, but it's still worse than using cash or gold. In which case you may have no traces of transactions left behind. If I was living under an oppressive regime, I'd be weary of using crypto instead of cash. However, the advantage that crypto has is to reduce control that democratic governments have over the economy. But it could actually be an asset in combating tax evasion. You'd be able to get a lot more with subpoenas and warrants.