Indian certificate authority provider eMudhra has revoked eight intermediate CAs following revelations that a script linked to its October key compromise incident unintentionally weakened those CAs’ private keys. Although these keys weren’t exposed through a traditional breach, a flaw in the key transfer process dropped each private key down to just a single leading byte in one critical step, rendering them vulnerable.
What Went Wrong: The Key Ceremony on April 30, 2025
During a key ceremony at eMudhra’s US and EU facilities using Crypto4A hardware security modules (HSMs), the company’s team attempted to move CA keys — among them 16 keys, including the eight affected by this newly disclosed issue. The keys were wrapped in one HSM, transferred to another, and then unwrapped. The script used for this task is where the problem arose.
The same script that handled keys for an earlier October compromise read them out of the HSM into a computer’s memory. For eight ECDSA private keys, one line of code truncated them to only their leading byte during recreation. Despite the altered, severely weakened private keys, certificates issued with them still worked, passed audits, and got linted without issue.
Scope, Response & Trust Fallout
Of the eight revoked intermediate CAs, six were tied to TLS (website security) and two to code signing. Four entered production in May. In total, nearly 200 certificates have been listed as issued by the affected CAs, including certificates tied to eMudhra’s own domains. Holders must now replace those certificates — most already have, the company says.
The company had initially deemed these particular CAs “unaffected,” based on their assessment that they bypassed the flawed script path. But revised analysis, discussions with browser root programs, and internal trouble reproducing how private key operations were managed forced a reassessment. Late last week, eMudhra revoked the eight CAs citing “cessationOfOperation”—not the more severe “keyCompromise” status used for prior revocations.
This incident compounds larger trust implications: emSign, eMudhra’s brand for public TLS certificates, is phasing out its public TLS operations after an announcement on October 22. Multiple browsers and platforms are withdrawing trust for eMudhra’s G1 root certificates, starting November 16 for Windows and Edge, and November 30 for Apple platforms. Some command-line tools will also reject certificates chaining to those roots.
An independent review by KPMG is underway and due by December 4, while an inventory of all CA keys is scheduled to wrap up by November 30. As of now, eMudhra states that there’s no evidence its weakened keys have been misused. Users concerned should check the company’s certificate list or Certificate Transparency logs for submissions from the revoked G2C TLS issuers.
This isn’t just a PKI operational failure — it’s a reminder of the fragility of trust. Human-oriented controls (scripts, processes) often sit behind what seem like mathematically secure systems, yet can destroy assurance entirely. With browsers rapidly cutting eMudhra off and cross-platform trust eroding, the clock is ticking for affected organizations to act before more damage is done.
