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+MODULI(5) File Formats Manual MODULI(5)
+
+NAME
+ moduli M-bM-^@M-^S Diffie-Hellman moduli
+
+DESCRIPTION
+ The /etc/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 -M generate,
+ calculates numbers that are likely to be useful. A second primality
+ testing pass, using ssh-keygen -M screen, 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,
+ containing seven space-separated fields. These fields are as follows:
+
+ timestamp The time that the modulus was last processed as
+ YYYYMMDDHHMMSS.
+
+ 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; 2p+1 is also prime.
+
+ Moduli candidates initially produced by ssh-keygen(1)
+ are Sophie Germain primes (type 4). Further 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 M-bM-^@M-^S not prime.
+ 0x02 Sieve of Eratosthenes.
+ 0x04 Probabilistic 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 the number of primality
+ trials that have been performed on the modulus.
+
+ size Decimal number indicating the size of the prime in
+ bits.
+
+ generator The recommended generator for use with this modulus
+ (hexadecimal).
+
+ 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/moduli that best meets the size requirement.
+
+SEE ALSO
+ ssh-keygen(1), sshd(8)
+
+STANDARDS
+ M. Friedl, N. Provos, and W. Simpson, Diffie-Hellman Group Exchange for
+ the Secure Shell (SSH) Transport Layer Protocol, RFC 4419, March 2006.
+
+OpenBSD 7.2 April 16, 2022 OpenBSD 7.2