LadderLeak: Side-channel security flaws exploited to break ECDSA cryptography

guest · May 28, 2020

LadderLeak: Side-channel security flaws exploited to break ECDSA cryptography
Existing attacks refined to attack elliptic curve algorithm
May 28, 2020
https://portswigger.net/daily-swig/...y-flaws-exploited-to-break-ecdsa-cryptography

Researchers have demonstrated how existing attacks against the ECDSA cryptographic algorithm can be improved to reduce the required nonce leakage by exploiting side-channel vulnerabilities.

No algorithm is protected against every form of exploit, and in ECDSA’s case it is possible to take advantage of the nonce that’s generated as part of the signing process.
A new method has now been proposed by academics from Aarhus University, the University of Campinas, the University of Adelaide, NTT, and Data61 that is able to break ECDSA with less than one bit of nonce leakage.
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Climbing the ladder
Published on May 25, the paper (PDF), penned by Diego Aranha, Felipe Rodrigues Novaes, Akira Takahashi, Mehdi Tibouchi, and Yuval Yarom, explores a new theoretical attack called ‘LadderLeak’.

“Due to the very sensitive nature of the [nonce] generated as part of the signing algorithm, it is known that any small amount of nonce exposure or nonce bias can in principle lead to a full key recovery: the key recovery is then a particular instance of Boneh and Venkatesan’s hidden number problem (HNP),” the researchers explain.
According to the researchers, this may be the first time that 192-bit ECDSA has been broken with one bit of leakage or less, and breaking P-224 with a one-bit leak – or P-256 with a two-bit leak – is possible using “relatively modest data complexity”.
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LadderLeak: Breaking ECDSA With Less Than One Bit Of Nonce Leakage

In this paper, we uncover LadderLeak, a novel class of side-channel vulnerabilities in implementations of the Montgomery ladder used in ECDSA scalar multiplication. The vulnerability is in particular present in several recent versions of OpenSSL.
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