Drive-by Key-Extraction Cache Attacks from Portable Code.

We show how malicious web content can extract cryptographic secret keys from the user’s computer. The attack uses portable scripting languages supported by modern browsers to induce contention for CPU cache resources, and thereby gleans information about the memory accesses of other programs running on the user’s computer. We show how this side-channel attack can be realized in WebAssembly and PNaCl; how to attain fine-grained measurements; and how to extract ElGamal, ECDH and RSA decryption keys from various cryptographic libraries.