Quantum randomness stays secure even when devices secretly leak signals

Bell tests for device-independent cryptography require that the two measurement devices can't communicate, but in practice perfect isolation is hard. This work shows that even when a noisy copy of one party's input leaks to the other before measurement, quantum nonlocality can still be certified. The authors fully map out the geometry of allowed classical correlations in this leaky scenario and find Bell inequalities that are actually more noise-tolerant than the standard CHSH inequality—good news for real-world quantum cryptography in tight quarters.