Re: OpenSSH authentication key length

From: Richard E. Silverman (
Date: 03/29/02

From: (Richard E. Silverman)
Date: 29 Mar 2002 02:56:13 -0500

> -b bits
> Specifies the number of bits in the key to create.
> Minimum is 512 bits. Generally 1024 bits is considered
> sufficient, and key sizes above that no longer improve
> security but make things slower. The default is 1024
> bits.
> But doesn't longer key provide stronger security?

Suppose that, according to the state of the art in computing hardware and
current understanding of practical attacks on a particular cipher, a n-bit
key requires longer than the age of the universe to crack. Then a 2n-bit
key does not increase security in any meaningful way, but simply slows
things down.

  Richard Silverman