Dangerous SHA-1 crypto function will die in SSH linking millions of computers



Enlarge (credit: Chaval Brasil )
Developers of two open source code libraries for Secure Shell—the protocol millions of computers use to create encrypted connections to each other—are retiring the SHA-1 hashing algorithm, four months after researchers piled a final nail in its coffin.
The moves, announced in release notes and a  code update for OpenSSH and libssh respectively, mean that SHA-1 will no longer be a means for digitally signing encryption keys that prevent the monitoring or manipulating of data passing between two computers connected by SSH—the common abbreviation for Secure Shell. (Wednesday's release notes concerning SHA-1 deprecation in OpenSSH repeated word for word what developers put in February release notes , but few people seemed to notice the planned change until now.)
“Chainsaw in a nursery”
Cryptographic hash functions generate a long string of characters that are known as a hash digest. Theoretically, the digests are supposed to be unique for every file, message, or other input fed into the function. Practically speaking, digest collisions must be mathematically infeasible given the performance capabilities of available computing resources. In recent years, a host of software and services have stopped using SHA-1 after researchers demonstrated practical ways for attackers to forge digital signatures that use SHA-1. The unanimous agreement among experts is that it's no longer safe in almost all security contexts.

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