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For the first time, researchers have demonstrated that a large portion of cryptographic keys used to protect data in computer-to-server SSH traffic are vulnerable to complete compromise when naturally occurring computational errors occur while the connection is being established.

Underscoring the importance of their discovery, the researchers used their findings to calculate the private portion of almost 200 unique SSH keys they observed in public Internet scans taken over the past seven years. The researchers suspect keys used in IPsec connections could suffer the same fate. SSH is the cryptographic protocol used in secure shell connections that allows computers to remotely access servers, usually in security-sensitive enterprise environments. IPsec is a protocol used by virtual private networks that route traffic through an encrypted tunnel.

The vulnerability occurs when there are errors during the signature generation that takes place when a client and server are establishing a connection. It affects only keys using the RSA cryptographic algorithm, which the researchers found in roughly a third of the SSH signatures they examined. That translates to roughly 1 billion signatures out of the 3.2 billion signatures examined. Of the roughly 1 billion RSA signatures, about one in a million exposed the private key of the host.

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In 2015, researchers reported a surprising discovery that stoked industry-wide security concerns—an attack called RowHammer that could corrupt, modify, or steal sensitive data when a simple user-level application repeatedly accessed certain regions of DDR memory chips. In the coming years, memory chipmakers scrambled to develop defenses that prevented the attack, mainly by limiting the number of times programs could open and close the targeted chip regions in a given time.

Recently, researchers devised a new method for creating the same types of RowHammer-induced bitflips even on the newest generation of chips, known as DDR4, that have the RowHammer mitigations built into them. Known as RowPress, the new attack works not by “hammering” carefully selected regions repeatedly, but instead by leaving them open for longer periods than normal. Bitflips refer to the phenomenon of bits represented as ones change to zeros and vice versa.

Further amplifying the vulnerability of DDR4 chips to read-disturbance attacks—the generic term for inducing bitflips through abnormal accesses to memory chips—RowPress bitflips can be enhanced by combining them with RowHammer accesses. Curiously, raising the temperature of the chip also intensifies the effect.