"PuTTY SSH Client Flaw Allows Recovery of Cryptographic Private Keys"
"PuTTY SSH Client Flaw Allows Recovery of Cryptographic Private Keys"
Fabian Baumer and Marcus Brinkmann from Ruhr University Bochum discovered a vulnerability in PuTTY 0.68 through 0.80 that enables attackers with access to 60 cryptographic signatures to recover the private key used to generate them. PuTTY is a popular open source terminal emulator, serial console, and network file transfer tool that supports SSH, Telnet, SCP, and SFTP. According to the researchers, the vulnerability stems from how PuTTY generates ECDSA nonces, which are temporary unique cryptographic numbers, for the NIST P-521 curve used for SSH authentication.