The PayWinner function of a simplelottery smart contract implementation for The Ethereum Lottery, an Ethereum gambling game, generates a random value with publicly readable variable maxTickets (which is private, yet predictable and readable by the eth.getStorageAt function). Therefore, it allows attackers to always win and get rewards.
The product uses a Pseudo-Random Number Generator (PRNG) in a security context, but the PRNG’s algorithm is not cryptographically strong.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| The_ethereum_lottery | Theethereumlottery | - (including) | - (including) |
When a non-cryptographic PRNG is used in a cryptographic context, it can expose the cryptography to certain types of attacks. Often a pseudo-random number generator (PRNG) is not designed for cryptography. Sometimes a mediocre source of randomness is sufficient or preferable for algorithms that use random numbers. Weak generators generally take less processing power and/or do not use the precious, finite, entropy sources on a system. While such PRNGs might have very useful features, these same features could be used to break the cryptography.