Indian certificate authority eMudhra defends weak signing keys, including one valued at '4'

Company blames a flaw in its key generation ceremony as the security industry warns of certificate forgery risk

By LineZotpaper

Published22 October 2026

Read Time2 min

Indian certification authority eMudhra has defended itself after it emerged that some private keys it used to sign digital certificates were trivially weak, with one key consisting of just the number "4" and several others short strings of easily guessed two or three digit numbers.

Because the key values are easy to deduce, an attacker could forge certificates and impersonate websites or other resources, a prize for scammers and phishers. The wider infosec industry has urged swift adoption of better certificates, while noting that implementing replacements will be a long and thankless task for those affected.

In a statement reported on Wednesday, eMudhra said the keys were generated during a Key Generation Ceremony held on April 30, 2025, using FIPS 140-2 Level 3 Hardware Security Modules, the standard equipment for the job. "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 said. "The weak keys were the ones published to the browser root stores. eMudhra is working to establish the root cause."

The company then struck a defensive tone, noting that "these roots and issuing CAs have gone through independent audits for two years in a row and have been in browser trust lists since mid-2025," a point that appears to shift some blame to auditors and other stakeholders. It also said its TLS business generates just one percent of its revenue, suggesting the incident will not materially affect its finances, a detail that does little for the organisations now facing an urgent, costly certificate replacement job.

"eMudhra is working directly with customers who may be affected to give them replacement certificates, so that critical services are not disrupted," the statement said, adding that the company is also working with the root programs and continuing its root cause investigation. It conceded the incident "may have some reputational risks on eMudhra which cannot be quantified."

Analysis

Why This Matters

Weak certificates' authority signing keys undermine the trust model that secures encrypted web traffic. If the keys can be guessed, certificates can be forged and websites impersonated.
Every organisation relying on eMudhra-issued certificates now faces an urgent, costly job replacing them and reviewing exposure.
The case raises questions about how such keys passed independent audits and earned placement in browser trust lists, putting auditors and root programs under scrutiny.

Background

Certification authorities sit at the heart of web security. Browsers and other software maintain root stores that determine which CAs are trusted to vouch for websites' identities. If a CA's signing keys are compromised, the certificates it issued can be forged, enabling phishing and other scams that appear to come from legitimate sites. eMudhra, an Indian certification authority, said its roots and issuing CAs have been in browser trust lists since mid-2025 after two consecutive years of independent audits.

Key Perspectives

eMudhra: The company blames a flaw in its key generation ceremony, which it says produced a second set of weak keys alongside the original strong keys, with the weak keys the ones published to browser root stores. It points to its audit record and trust list membership, and emphasises that TLS is only a small part of its business. The security industry: Researchers say the keys are trivially guessable, making certificate forgery straightforward, and have urged swift replacement of the affected certificates, warning that doing so will be a lengthy task. Customers and relying parties: Organisations holding eMudhra-issued certificates now face an unwanted and costly scramble to obtain replacements so critical services are not disrupted, and to assess whether they have been exposed to forgery.

What to Watch

The outcome of eMudhra's root cause investigation into how the key generation ceremony produced a second, weak set of keys.
Whether browser root programs take action, including possible removal of eMudhra roots from trust stores if the investigation is not reassuring.
The pace of replacement certificate issuance to affected customers, and any reports of certificates actually being forged in the wild before the weakness was disclosed.

Sources

Certification authority eMudhra defends its laughably weak private keys · www.theregister.com - Articles

Checked

11 claims in this story checked against 1 source: 10 supported.

Show each claim

SupportedOne key used to sign certificates was the number “4.”www.theregister.com - Articles: “one was literally just the number “4,””
SupportedeMudhra’s statement said a flaw in the Key Generation Ceremony produced weak keys alongside the original strong keys.www.theregister.com - Articles: ““A flaw in the KGC caused a wrap/unwrap step to produce a second set of weak keys alongside the original strong keys,” the statement claims.”
SupportedThe company said the weak keys were published to browser root stores and it was working to establish the root cause.www.theregister.com - Articles: ““The weak keys were the ones published to the browser root stores. eMudhra is working to establish the root cause.””
SupportedThe summary says the security industry warned of certificate-forgery risk.www.theregister.com - Articles: “It’s easy to deduce the value of those keys, which makes it possible to forge certs and impersonate websites or other resources. That’s gold for scammers, phishers, and other miscreants. The entire infosec industry has pointed that out”
SupportedThe statement said the roots and issuing CAs had passed independent audits for two years in a row and had been on browser trust lists since mid-2025.www.theregister.com - Articles: ““These roots and issuing CAs have gone through independent audits for two years in a row and have been in browser trust lists since mid-2025,” the statement adds”
SupportedThe statement said eMudhra was working directly with potentially affected customers to provide replacement certificates so critical services would not be disrupted.www.theregister.com - Articles: ““eMudhra is working directly with customers who may be affected to give them replacement certificates, so that critical services are not disrupted.”
SupportedThe company said the incident may pose reputational risks that cannot be quantified.www.theregister.com - Articles: “The company allows that the incident “may have some reputational risks on eMudhra which cannot be quantified.””
Not in the sourcesThe statement was reported on Wednesday.
SupportedThe key-generation ceremony took place on April 30, 2025, using FIPS 140-2 Level 3 Hardware Security Modules.www.theregister.com - Articles: ““a Key Generation Ceremony (KGC) held on April 30, 2025, using FIPS 140-2 Level 3 Hardware Security Modules (HSMs).””
SupportedThe weak keys could be used to forge certificates and impersonate websites or other resources.www.theregister.com - Articles: “It’s easy to deduce the value of those keys, which makes it possible to forge certs and impersonate websites or other resources.”
SupportedeMudhra’s TLS business generates one percent of its revenue, suggesting the incident would not affect its bottom line much.www.theregister.com - Articles: “The announcement then points out that eMudhra’s TLS business generates just one percent of its revenue, meaning this mess won’t impact its bottom line too much.”