(from a research paper by F. Dörre and V. Klebanov) The bitcoin theft incident. The presumed genesis of the attack is as follows: Bitcoin operates a public da

(from a research paper by F. Dörre and V. Klebanov) The bitcoin theft incident. The presumed genesis of the attack is as follows: Bitcoin operates a public database of all transactions, the block chain. Each transaction is cryptographically signed by its initiator using the ECDSA scheme. Creating ECDSA signatures requires a per-transaction nonce. Partial predictability of nonces allows for one class of attacks, but using the same nonce for two transactions signed by the same key---which is what probably happened---constitutes a catastrophic security failure. Anyone can easily identify this case from the information recorded in the block chain, reconstruct the victim’s private key, and divert their money to a bitcoin address of choice. No intrusion into the victim’s system is necessary. A loss of seed entropy in the PRNG used for generating nonces increases the probability of the breach. This ultimately caused Google to replace the Android PRNG, which was only providing 40% of the requested entropy for this particular use. ----- I also recall someone had discovered an online poker service's shuffle algorithm was something common (maybe Fisher-Yates?) based on java.util.Random with system time as a seed. Once you see your own hand and part of the board, you get a fairly accurate idea of what could be in someone else's hand from the small-ish sample of possible deals around system time.