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diff --git a/moduli.0 b/moduli.0 new file mode 100644 index 0000000..3077643 --- /dev/null +++ b/moduli.0 @@ -0,0 +1,74 @@ +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 7.3 April 16, 2022 OpenBSD 7.3 |