That is not the type of log level security we are discussing. "Security" here means that a piece of data that was written to the log stays there unaltered. "T

That is not the type of log level security we are discussing. "Security" here means that a piece of data that was written to the log stays there unaltered. "Theft" is on a much higher abstraction level. A "Bitcoin theft" is that someone steals your key and then appends a message to the log "Boplicity pays 17 BTC to Joe. Signed: Boblicity". Stealing your private key does not take place on the blockchain. And all previous entries to the log are still there.