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openssh-client_5.9p1-5ubuntu1_i386 **NAME**

**moduli** — Diffie-Hellman moduli

**DESCRIPTION**

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,
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; (p+1)*2 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 – 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/ssh/moduli__ that best meets the size
requirement.

**SEE** **ALSO**

ssh-keygen(1), sshd(8)
__Diffie-Hellman__ __Group__ __Exchange__ __for__ __the__ __Secure__ __Shell__ __(SSH)__ __Transport__ __Layer__
__Protocol__, RFC 4419, 2006.