New Device Passkey Bootstrap via PRF Exchange with Anomalous Signal Correlation
Detects new-device passkey bootstrap via PRF exchange and encrypted passkey download correlated with an anomalous signal (no prior authentication history on the device, new geolocation/ASN, or missing user-presence confirmation on the trusted device), consistent with an attacker abusing the one-time cross-device sync bootstrap flow to sync a victim's passkeys to an attacker-controlled device.
Sigma
