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The endCoinFlip function and throwSlammer function of the smart contract implementations for Cryptogs, an Ethereum game, generate random numbers with an old block's hash. Therefore, attackers can predict the random number and always win the game.
The endCoinFlip function and throwSlammer function of the smart contract implementations for Cryptogs, an Ethereum game, generate random numbers with an old block's hash. Therefore, attackers can predict the random number and always win the game.
CVSS 3.0 Base Score 7.5. CVSS Attack Vector: network. CVSS Attack Complexity: low. CVSS Vector: (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N).
CVSS 2.0 Base Score 5. CVSS Attack Vector: network. CVSS Attack Complexity: low. CVSS Vector: (AV:N/AC:L/Au:N/C:P/I:N/A:N).
Both of these examples use a statistical PRNG to generate a random number:
int accountID = random.nextInt();
int randNum = rand();The random number functions used in these examples, rand() and Random.nextInt(), are not considered cryptographically strong. An attacker may be able to predict the random numbers generated by these functions. Note that these example also exhibit CWE-337 (Predictable Seed in PRNG).
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