Indian CA eMudhra confirms eight TLS certificates with critically weak private keys

A security analysis of certificates issued by the Indian certificate authority eMudhra Limited revealed eight TLS certificates with critically weak private keys, ranging from 3 to 8 bits of entropy. In contrast, a secure NIST P-384 elliptic curve private key contains roughly 384 bits of entropy, providing approximately 2^384 possible values.

The compromised keys were so weak that security engineers described the situation as "challenging the imagination," with key sizes of 4, 56, 66, 115, 155, 156, 230, and 237 bits reported. The immediate threat is most acute for users relying on VPNs, particularly in regions where state-level actors may conduct man-in-the-middle interceptions.

Exploitation requires an adversary to perform an active man-in-the-middle attack, positioning themselves between TLS endpoints to decrypt, inspect, and re-encrypt traffic. While such capabilities are typically limited to well-resourced attackers, local network control—such as in a coffee shop or university—can suffice for interception.

eMudhra has not publicly detailed the root cause, but subsequent reporting on the Mozilla issue tracker suggests the issue stemmed from a script that failed to use a hardware security module (HSM) for key signing, despite using the correct HSM device for key generation. The error went undetected even when cross-signing intermediates with the incorrect root certificate.

The incident has prompted eMudhra to announce its voluntary withdrawal from the global SSL/TLS certificate business, refocusing on other digital trust services. The company did not respond to requests for comment at the time of reporting.

Security experts argue the episode highlights systemic weaknesses in certificate revocation and monitoring. Transparency logs can detect unauthorized certificates only after issuance, and revocation mechanisms often depend on clients actively monitoring massive feeds. Many embedded and legacy systems may never receive updated certificates, prolonging exposure.