How eMudhra's compromised certificates put web's system of trust at risk

Eight eMudhra intermediate certificates had weak private keys that could enable website impersonation, prompting Google, Mozilla and Cloudflare to act to protect internet users

Imagine opening a banking website, entering a password and seeing the familiar padlock next to the web address. The browser indicates that the connection is secure. But how does it know that the website really belongs to the bank? It relies on digital certificates issued by trusted organisations.

 

A security failure involving Indian company eMudhra has raised concerns about this system after eight intermediate certificates were found to have weak private keys that attackers could work out. These keys could be used to create fake certificates and impersonate websites.

 

Browser makers Google and Mozilla, along with Cloudflare, a web infrastructure company, have responded with measures to block the affected certificates. India's Computer Emergency Response Team (CERT-In) has also issued an advisory warning that the compromised keys could be used to impersonate websites and potentially intercept or alter online communications, according to details reported by PTI.

In a statement issued on October 21, eMudhra said a flaw in its key-generation process created the weak keys, while maintaining that its infrastructure was not compromised and no Indian data was breached. The company said its investigation into the cause was continuing.

What is eMudhra and what does it do

eMudhra is an Indian digital trust company that provides digital certificates and services for verifying identities and securing online transactions. It operates as a certificate authority (CA), an organisation that issues digital certificates to help websites and other entities prove their identity online.

 

A digital certificate works much like an identity card for a website. When someone visits a banking website, for example, the browser checks its certificate to help establish that it is connecting to the genuine website rather than an impostor. Certificate authorities issue these certificates, which browsers use to determine whether a website's identity can be trusted.

 

eMudhra also provides digital signature certificates and electronic signing services that allow people and businesses to sign documents online. The company is listed by the Controller of Certifying Authorities (CCA), the government body responsible for licensing and regulating certifying authorities in India. It is also associated with Aadhaar-linked electronic know-your-customer (e-KYC) services, according to the Unique Identification Authority of India (UIDAI).

 

eMudhra is not the only company authorised to issue digital certificates in India. The CCA's list includes other providers such as Protean, C-DAC, Capricorn and VSign. Their services vary, but they operate within India's regulated digital-signature ecosystem.

Why do websites need security certificates

When someone visits a website, the browser needs to check that it is connecting to the genuine website and that information exchanged with it is protected from being read or altered by others.

 

This is where HTTPS (Hypertext Transfer Protocol Secure) comes in. It helps secure the connection between a website and a browser using a system called Transport Layer Security (TLS). As part of this process, the website presents a digital certificate that helps the browser verify its identity.

 

The digital certificate links the website's name to a public key, while the website keeps a matching private key secret. The browser checks the certificate to see whether it was issued by an authority it trusts and whether it is valid.

If these checks succeed, the browser can establish an encrypted connection. This helps protect information such as passwords, payment details and private messages as they travel across the internet.

 

However, a secure connection does not guarantee that a website is legitimate or that its content is safe. It helps confirm the website's identity and protects information exchanged with it, but a fraudulent website can also have a valid security certificate.

What went wrong at eMudhra

Certificate authorities operate through a hierarchy. At the top is a root certificate authority, whose certificate is trusted by browsers or operating systems. It can authorise intermediate certificate authorities to issue certificates to websites.

 

A problem with an intermediate authority can affect the websites relying on it, even if those websites themselves have not been hacked.

 

According to Google and Mozilla, the private keys linked to eight eMudhra intermediate certificates were generated with insufficient randomness, making them possible to recover.

 

In its statement, eMudhra said the eight affected intermediate authorities were created on April 30, 2025, using specialised hardware designed to generate and protect cryptographic keys. The company said a flaw in the key-generation process caused a step used to protect and handle the keys to produce a second set of weak keys alongside the original strong ones. According to eMudhra, the weak keys were published to browser root stores. The company said it was still investigating the cause of the flaw.

 

Information shared by Indian cybersecurity consulting firm Security Brigade said the eight private keys, which were expected to have approximately 116 digits of cryptographic strength, were found to be numbers as small as four. This made it possible to recover the keys rather than having to break the encryption through the usual computational methods.

 

An attacker who obtains one of these private keys could use it to create certificates that appear to have been issued by the affected authority, potentially allowing the impersonation of websites.

 

eMudhra said an independent researcher discovered the weakness over the weekend and reported it to the root programmes operated by Apple, Google, Microsoft and Mozilla.

How could attackers misuse the keys

The Indian Computer Emergency Response Team (CERT-In), the government agency responsible for responding to cybersecurity incidents, has warned about the risks arising from the compromised certificates. According to details of its advisory reported by PTI, attackers could use the affected private keys to create fraudulent certificates, impersonate legitimate websites and potentially intercept or modify communications.

 

For example, an attacker might try to impersonate a bank's website. If the attacker can intercept a user's connection and present a fake certificate signed using a compromised key, a browser that still trusts that certificate could accept the fake website as genuine.

 

The attacker could then potentially intercept information exchanged through that connection, including login details.

 

Possessing a compromised key does not automatically give an attacker access to bank accounts or passwords. The attacker would also need a way to intercept or redirect the connection, and the browser or application would need to fail to reject the fraudulent certificate.

 

Google has also pointed to Certificate Transparency, a system that records publicly trusted website certificates in logs that security teams can inspect. Google said no TLS certificates issued through six of the affected intermediate certificates had been recorded in these logs before its blocking action.

What has eMudhra said about the impact

eMudhra said the incident was limited to eight intermediate certificate authorities used in its global TLS business. The company said its own infrastructure had not been compromised, no data had been breached and its physical and digital security controls remained intact.

 

The company also stressed that its Indian digital signature and eSign services were not affected. These services are used for tasks such as digitally signing documents and completing electronic verification processes. According to eMudhra, its Indian digital signature and eSign operations run on separate infrastructure from the affected global TLS business and continue to function normally.

 

The affected business accounts for around 1 per cent of eMudhra's revenue, the company said. However, it acknowledged that the incident could carry reputational risks.

How have browsers and other internet services responded

Browser makers Google and Mozilla have taken steps to stop their products from trusting certificates linked to the incident.

 

Google said it had updated Chrome to block certificates linked to the affected eMudhra authorities. Users do not need to update or restart the browser for this protection to take effect.

 

Mozilla said it had added the affected certificates to a blocklist, which tells Firefox not to trust them. The company said this update reached users with standard browser settings within three hours of the report. Mozilla also announced security updates and changes to how Firefox handles trusted certificates.

 

Cloudflare, a company that helps websites manage internet traffic and protect against cyber threats, said it began rolling out protections across its network on October 19. It also issued updates for some of its applications and services.

 

Cloudflare said its investigation had found no evidence that attackers were actively exploiting the weakness in its services.

 

However, these steps do not automatically protect every device connected to the internet. Some devices, network equipment and business software use their own systems to check whether a website's certificate can be trusted. They may need separate updates to recognise the affected certificates as unsafe.

Why could some devices remain at risk

Browsers such as Chrome and Firefox can receive lists of blocked certificates without waiting for a full software update. Other systems may not have this facility.

 

Businesses use certificates to secure internal applications, APIs, servers and network equipment. Smart devices and other connected products also rely on certificates to identify the systems they communicate with.

 

Some products use the operating system's certificate store, while others have their own lists of trusted authorities built into their software. Updating a browser may not fix the problem for other applications running on the same device.

 

According to Cert-IN advisory, reported by PTI, the govt body has recommended that organisations update affected browsers, applications and operating systems, check their lists of trusted certificates and identify websites and services that rely on the affected intermediate authorities. Organisations may need to obtain replacement certificates where necessary and verify that the certificates their systems rely on remain valid.

 

The advisory also calls for a review of certificates linked to the emSign ECC Root CA - G3. Google has announced plans to remove trust in this root certificate in Chrome, a change that could affect some legitimate websites and services using certificates issued under it.

 

These checks may be more difficult for older devices that no longer receive software updates. Organisations may need to assess which systems are affected and determine whether they can be updated or require other remedial action.

 

Yash Kadakia, founder and chief technology officer (CTO) of Security Brigade, in a note shared with Business Standard said the incident exposed a wider weakness in the internet's system of trust.

 

"This isn't just about eight compromised keys. It's about the global internet's chain of trust. 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," he said.

 

Kadakia also called for CERT-In and India's regulators to review the effectiveness of mandatory security audits, questioning how such cryptographic weaknesses escaped detection