Possession of these keys could have allowed anyone to issue certificates for websites across the internet, including bank websites and government portals.
A Bengaluru-based company trusted by major web browsers to authenticate websites generated eight security certificates with private keys so weak that they could be recovered within seconds. Google, Mozilla, Apple and Microsoft have blocked the certificates, while the Union government has formed a special team to investigate the incident.
The keys belonged to the listed certifying authority eMudhra Ltd. Instead of being randomly generated numbers roughly 116 digits long, the keys were so weak that one of them was simply the number 4.
Possession of these keys could have allowed anyone to issue certificates for websites across the internet, including bank websites and government portals. Such certificates act as digital identity cards, allowing browsers, phones and computers to verify a website’s identity and treat it as genuine.
No evidence has emerged so far that the keys were misused. The major browsers also had a safeguard that would have exposed attempts to target their users. However, security experts have warned that the lapse undermines “the global internet’s chain of trust”.
Since a trusted certificate authority can authenticate any website, a failure at one company could affect organisations that have never dealt with it directly. Experts warned that the weak keys could provide phishing gangs and eavesdroppers with an opportunity to exploit the system, the Hindustan Times reported.
The remediation process could be extensive, particularly for routers, payment terminals and older software that are not regularly updated.
“As this incident enables even technically unsophisticated individuals to easily recover the private keys for these intermediates, the impact of this incident could not be higher,” Mozilla, which develops the Firefox browser, said in its incident report.
eMudhra Attributes Weak Keys To Flaw In Key Generation Process
In a statement issued on Wednesday, eMudhra said, “A flaw in the KGC caused a wrap/unwrap step to produce a second set of weak keys alongside the original strong keys”. The company was referring to the key generation ceremony conducted on April 30, 2025, when the defective keys were created.
“The weak keys were the ones published to the browser root stores,” it said.
eMudhra maintained that its infrastructure had not been compromised and no data had been breached. It added that its Indian digital signature certificate and eSign businesses operate on separate infrastructure and were unaffected.
MeitY Forms Special Team,
CERT-In
Warns Of Potential Cyberattacks
The Ministry of Electronics and Information Technology (MeitY) said it had “taken serious note” of the incident and constituted a special team to investigate it. According to the ministry, the impact on Indian websites and applications had been “very limited and for a very short interval”.
The ministry also accused some social media accounts of “fear-mongering” over the incident.
However, the basis for the ministry’s assessment of the impact was not clear. The keys could potentially have been exploited at any point after April 2025. Moreover, forged certificates used against applications, servers or devices that do not check Certificate Transparency logs would not necessarily appear in public records.
The Indian Computer Emergency Response Team (CERT-In), the country’s national cybersecurity agency, issued an advisory on Wednesday afternoon. It said the keys “were generated with insufficient cryptographic randomness” and “could be recovered almost instantly”.
CERT-In warned that attackers could exploit the keys to intercept or alter communications, “potentially resulting in credential theft, unauthorised disclosure of sensitive information and financial fraud”.
The agency urged government departments, internet service providers, software vendors and website administrators to update their systems and trusted certificate lists. It also cautioned users and administrators: “Do not bypass certificate-validation warnings or disable certificate verification.”
Cybersecurity Experts Warn Of Phishing And Man-In-The-Middle Attacks
Pete Membrey, chief research officer at ExpressVPN, which operates a virtual private network service, said some of the keys were “as small as a single byte, which is hard to explain”.
“None of the standard tools would ever let you create a key like that, so it sounds like they built something custom. It’s a textbook case of why the security world warns against building your own encryption tools rather than using proven ones,” he said.
Membrey described the incident as “a nightmare scenario for phishing and man-in-the-middle attacks”.
“Everyone is working hard and fast to get these certificates revoked. The problem is that many legitimate certificates are already out there, and people are depending on those too, so cleaning this up won’t be quick or simple,” he said.
Yash Kadakia, founder and chief technology officer of cybersecurity firm Security Brigade, said the consequences extended beyond the eight keys.
“This isn’t just about eight compromised keys. It’s about the global internet’s chain of trust,” he said. “A single authority’s failure can undermine authentication for organisations that have never dealt with it. The cleanup could be enormous, particularly for devices and software that cannot be easily updated.”
How The Chain Of Trust Works
Websites using addresses that begin with “https” present digital certificates to establish their identity. For instance, a certificate for sbi.co.in allows a browser to verify that the website belongs to the State Bank of India before displaying a padlock and encrypting information sent by the user.
A browser trusts the certificate because it has been signed by a certificate authority, a company responsible for verifying who controls a website. Browsers and operating systems maintain their own lists of trusted authorities, numbering several dozen, and eMudhra features on the lists maintained by Google, Mozilla, Apple and Microsoft.
Certificate authorities use top-level root certificates to sign intermediate certificates, which then sign certificates issued to individual websites. All eight affected eMudhra certificates were intermediates. Six were intended for websites, while the remaining two were used for code signing, a process through which software developers establish that a program is genuine.
If a website certificate functions as an identity card, an intermediate certificate authority acts like the office that issues those cards. Anyone possessing its private key — the secret number used to sign certificates — could potentially issue a certificate in the name of any website.
The browsers avoided the impact because they require website certificates to appear in Certificate Transparency logs, which are public records where forged certificates would have been visible.
How eMudhra’s Weak Keys Were Discovered
Under the encryption method used by eMudhra, private keys should be selected randomly from a range containing more numbers than the estimated number of atoms in the observable universe.
However, the company’s eight keys were 4, 56, 66, 115, 155, 156, 230 and 237. Dennis Jackson, a cryptography engineer at Mozilla who handled the incident, described them as “effectively all-zeroes apart from the last byte”.
Mozilla engineers recovered the keys by generating the first 256 possible keys and checking them against the affected certificates. Jackson also said that the AI agents he tested managed to recover them “on their first attempt with a simplistic prompt”.