eMudhra CA Private Keys Recovered Due to Weak Integer Values, Prompting Revocations

A researcher found that the private keys behind eight eMudhra intermediate certificates are integers under 256, far too small to be secure for P-384 keys. Using a simple brute-force search, the researcher recovered all eight keys in milliseconds and verified them against the published certificates and signatures. The flaw traces to a key ceremony in which a second, weak key pair was created on the hardware security module during an approved test, and those keys were used in certificate requests. Six of the affected intermediates are TLS certificates and two are code-signing, and their cross-signed copies were revoked in October 2025 with the reason ca_compromise. Earlier CRL signature failures in May 2025 had signaled a problem about sixteen months before the disclosure.