eMudhra Limited, an India-based certificate authority, is exiting the global SSL/TLS business after disclosing that it issued eight intermediate TLS certificates with critically weak private keys—one as low as 4 bits—that could be cracked in milliseconds.
Chairman V. Srinivasan cited three factors: rising compliance costs, SSL/TLS generating just 1 percent of company revenue, and competition from free certificate providers. "The level of social media amplification around this incident has brought scrutiny that is out of proportion to SSL/TLS's place in our business," eMudhra said in a statement Thursday.
The weakness in the certificates exposed major browsers, email servers, IoT devices, Docker containers, and Linux machines to risk. Malicious actors could have generated TLS certificates trusted across these platforms using the compromised intermediate credentials.
The certificates were supposed to use NIST P-384 elliptic curve cryptography, requiring 384 bits of entropy and producing 2^384 possible key combinations (a number with 116 digits). The actual private keys ranged from 3 to 8 bits. The eight weak keys identified: 4, 56, 66, 115, 155, 156, 230, and 237. Browser makers blocked certificates issued with these credentials within a day or two of discovery.
eMudhra almost certainly faced loss of its certificate authority status from the CA/Browser Forum, the industry body that governs admission to the TLS certificate program. Such a sanction would have been fatal to the company's credibility in the sector.
The company attributed the flaw to a malfunction in the wrap/unwrap step of a Key Generation Ceremony held April 30, 2025. The process used FIPS 140-2 Level 3 Hardware Security Modules, specialized devices designed to store encryption keys and sensitive data isolated from most networks. eMudhra said a second set of weak keys was produced alongside the intended strong keys, and the weak keys were subsequently published to browser root stores. The company is investigating the root cause.
