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Computational Errors in SSH Connections Expose Private Keys

As one of the most widely deployed protocols for remote access and secure administration, SSH needs little introduction.

For the first time, researchers demonstrated that a large portion of cryptographic keys used to protect data in computer-to-server SSH traffic is vulnerable and were able to calculate the private portion of almost 200 unique SSH keys they observed in public Internet scans [*].

The vulnerability occurs when there are errors during the signature generation 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, translating to about 1 billion signatures, about one in a million of which exposed the host’s private key. This attack is significant because it could allow attackers to eavesdrop on or modify encrypted SSH traffic.

Said UCSD (University of California, San Diego)’s Keegan Ryan, “Our research reiterates the importance of defense in depth in cryptographic implementations and illustrates the need for protocol designs that are more robust against computational errors.”

[*] https://arstechnica.com/security/2023/11/hackers-can-steal-ssh-cryptographic-keys-in-new-cutting-edge-attack/