Key Highlights
- Ledger said its certified TRNG-based seed generation prevented the type of entropy flaw that affected certain Coldcard devices.
- The Coldcard firmware bug caused some wallets to generate seeds using a weak software PRNG, contributing to thefts totaling millions.
- Ledger highlighted its AIS-31, Common Criteria, and ANSSI certifications, while stressing that independent validation strengthens hardware wallet security.
Ledger, the hardware wallet manufacturer, explained how its true random number generator (TRNG) design differs from the seed generation process affected by the recent Coldcard wallet vulnerability. The Coldcard incident, linked to a firmware bug introduced in March 2021, resulted in the theft of approximately 1,367 BTC, valued at around $88.6 million.
In an X post on Monday, Ledger said the incident highlighted the importance of reliable randomness in cryptocurrency self-custody and explained how its devices generate recovery seeds using certified hardware-based entropy sources.
How Ledger’s TRNG system works
Ledger said its devices generate seeds using a true random number generator embedded in a certified secure element. Unlike software-based solutions, the TRNG leverages chaotic physical phenomena on silicon to produce genuine entropy. The company said raw entropy generated by the TRNG is processed through cryptographic methods within Ledger OS before being used for seed generation.
Ledger added that its TRNG has been evaluated under the AIS-31 standard and certified under the PTG.2 requirements. Its Secure Elements also carry Common Criteria certifications at EAL5+ or EAL6+ levels, depending on the device model.
The company also noted that its devices have received ANSSI CSPN certification, with random number generation quality included in security evaluations. Ledger said these certifications allow security processes to be independently reviewed, although it acknowledged that no hardware wallet can eliminate all potential risks.
How the Coldcard incident unfolded
The Coldcard incident stemmed from a firmware bug introduced in a March 2021 commit. Instead of relying on the device’s hardware random number generator (RNG) for creating recovery seeds, a build configuration flaw caused some units to silently fall back to a weak software pseudorandom number generator (PRNG).
This fallback used predictable inputs, the chip’s serial number and timer values, drastically reducing entropy. Researchers estimate that over 1,000 BTC were drained from approximately 1,200 affected wallets. The vulnerability remained undetected in shipped firmware for five years.
Galaxy Research’s Alex Thorn reported what appears to be a fourth wave of organized thefts targeting Coldcard users. As of August 3, the confirmed portion of this latest sweep had moved 388.93 BTC across 218 transactions from 462 victim addresses.
Combined with waves 1, 2, and 3, total stolen funds reached approximately 1,367 BTC, valued at around $88.6 million, affecting thousands of addresses. The attacks demonstrated sophisticated patterns, with attackers precomputing vulnerable keys and sweeping funds on-chain.
Hardware wallets remain at risk
Despite Ledger’s detailed explanation, the Coldcard incident highlights ongoing risks inherent in hardware wallets, even from established manufacturers.
While certifications and hardware-based security measures can reduce certain risks, they do not eliminate vulnerabilities arising from firmware issues, implementation errors, or other attack methods.
The incident also highlights the importance of independent reviews, secure development practices, and ongoing monitoring for self-custody solutions holding digital assets.
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