MODULI man page on JazzOS

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MODULI(5)		  OpenBSD Programmer's Manual		     MODULI(5)

     moduli - Diffie Hellman moduli

     The /etc/ssh/moduli file contains prime numbers and generators for use by
     sshd(8) in the Diffie-Hellman Group Exchange key exchange method.

     New moduli may be generated with ssh-keygen(1) using a two-step process.
     An initial candidate generation pass, using ssh-keygen -G, calculates
     numbers that are likely to be useful.  A second primality testing pass,
     using ssh-keygen -T provides a high degree of assurance that the numbers
     are prime and are safe for use in Diffie Hellman operations by sshd(8).
     This moduli format is used as the output from each pass.

     The file consists of newline-separated records, one per modulus, contain-
     ing seven space separated fields.	These fields are as follows:

	   timestamp	The time that the modulus was last processed as YYYYM-

	   type		Decimal number specifying the internal structure of
			the prime modulus.  Supported types are:

			0     Unknown, not tested
			2     "Safe" prime; (p-1)/2 is also prime.
			4     Sophie Germain; (p+1)*2 is also prime.

			Moduli candidates initially produced by ssh-keygen(1)
			are Sophie Germain primes (type 4).  Futher primality
			testing with ssh-keygen(1) produces safe prime moduli
			(type 2) that are ready for use in sshd(8).  Other
			types are not used by OpenSSH.

	   tests	Decimal number indicating the type of primality tests
			that the number has been subjected to represented as a
			bitmask of the following values:

			0x00  Not tested
			0x01  Composite number - not prime.
			0x02  Sieve of Eratosthenes
			0x04  Probabalistic Miller-Rabin primality tests.

			The ssh-keygen(1) moduli candidate generation uses the
			Sieve of Eratosthenes (flag 0x02).  Subsequent
			ssh-keygen(1) primality tests are Miller-Rabin tests
			(flag 0x04).

	   trials	Decimal number indicating of primaility trials that
			have been performed on the modulus.

	   size		Decimal number indicating the size of the prime in

	   generator	The recommended generator for use with this modulus

	   modulus	The modulus itself in hexadecimal.

     When performing Diffie Hellman Group Exchange, sshd(8) first estimates
     the size of the modulus required to produce enough Diffie Hellman output
     to sufficiently key the selected symmetric cipher.	 sshd(8) then randomly
     selects a modulus from /etc/ssh/moduli that best meets the size requirement.

     ssh-keygen(1), sshd(8),

     Diffie-Hellman Group Exchange for the Secure Shell (SSH) Transport Layer
     Protocol, RFC 4419, 2006.

OpenBSD 4.5			 June 26, 2008				     2

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