Charles Guillemet

He designed Tiempo secure chips, then became CEA ITSEF technical manager.⁠[1]

He joined Ledger as CSO in 2017, creating its security department and Donjon.⁠[2][1]

In a February 28, 2019 interview, he described bug bounties as a way to invite outside researchers to test products and find problems an internal team might miss. The discussion covered hardware and software, recovery-phrase protection, PIN security and application isolation. He emphasized fixing reported weaknesses and rewarding researchers.⁠[3]

Ledger named him CTO on December 5, 2019.⁠[2]

On May 17, 2023, he discussed concerns about control over keys in a Big Whale interview about Ledger Recover. He described recovery as an optional service and acknowledged that firmware could already access the seed phrase. Reflecting on communication, he said he would have introduced the product before releasing the update notes.⁠[4]

In a March 24, 2026 essay, he argued that AI lowers the cost of finding and exploiting vulnerabilities, weakening defenders’ economic advantage. He advocated secure hardware, zero-knowledge proofs and formal verification, acknowledging cost and skills barriers. He emphasized supply-chain integrity and prompt patching for existing systems.⁠[5]

In an August 2, 2026 article, he emphasized high-quality randomness and described Ledger’s reliance on Secure Elements, hardware random-number generation and independent evaluation. He acknowledged that these measures do not confer immunity from attack. He also argued that AI is shortening the interval between disclosure and exploitation, making faster remediation necessary.⁠[6]

Ledger (Hardware Wallet Company)Ledger (Hardware Wallet Company)Ledger is a crypto-asset hardware wallet company headquartered in Paris, France, founded in 2014 by eight people including Eric Larchevêque. It is known for its secure-chip-based Ledger Nano hardware wallets and also offers the Ledger Wallet app (formerly Ledger Live) and Ledger Enterprise services for institutions. It is one of the largest hardware wallet makers and has been through security incidents including a 2020 customer data breach, the 2023 Connect Kit supply-chain attack, and the 2026 discovery of spying hardware implanted in devices sold through resellers.Open the full entry: Official website: https://www.ledger.com/ (opens in a new window)⁠[2]

X @P3b7_: Official account: https://x.com/P3b7_ (opens in a new window)⁠[7]

LinkedInLinkedInLinkedIn is a social networking platform for professionals. It was founded in 2002 by Reid Hoffman and others, launched in 2003, and listed on the New York Stock Exchange in 2011; after Microsoft acquired it for approximately $26.2 billion in 2016, it became a wholly owned Microsoft subsidiary. Its revenue comes from membership subscriptions, advertising, and recruitment solutions.Open the full entry: Official account: https://www.linkedin.com/in/charles-guillemet/ (opens in a new window)⁠[1]