1GENRSA(1)                           OpenSSL                          GENRSA(1)
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NAME

6       genrsa - generate an RSA private key
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SYNOPSIS

9       openssl genrsa [-out filename] [-passout arg] [-des] [-des3] [-idea]
10       [-f4] [-3] [-rand file(s)] [-engine id] [numbits]
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DESCRIPTION

13       The genrsa command generates an RSA private key.
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OPTIONS

16       -out filename
17           the output filename. If this argument is not specified then
18           standard output is used.
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20       -passout arg
21           the output file password source. For more information about the
22           format of arg see the PASS PHRASE ARGUMENTS section in openssl(1).
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24       -des|-des3|-idea
25           These options encrypt the private key with the DES, triple DES, or
26           the IDEA ciphers respectively before outputting it. If none of
27           these options is specified no encryption is used. If encryption is
28           used a pass phrase is prompted for if it is not supplied via the
29           -passout argument.
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31       -F4|-3
32           the public exponent to use, either 65537 or 3. The default is
33           65537.
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35       -rand file(s)
36           a file or files containing random data used to seed the random
37           number generator, or an EGD socket (see RAND_egd(3)).  Multiple
38           files can be specified separated by a OS-dependent character.  The
39           separator is ; for MS-Windows, , for OpenVMS, and : for all others.
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41       -engine id
42           specifying an engine (by its unique id string) will cause genrsa to
43           attempt to obtain a functional reference to the specified engine,
44           thus initialising it if needed. The engine will then be set as the
45           default for all available algorithms.
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47       numbits
48           the size of the private key to generate in bits. This must be the
49           last option specified. The default is 512.
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NOTES

52       RSA private key generation essentially involves the generation of two
53       prime numbers. When generating a private key various symbols will be
54       output to indicate the progress of the generation. A . represents each
55       number which has passed an initial sieve test, + means a number has
56       passed a single round of the Miller-Rabin primality test. A newline
57       means that the number has passed all the prime tests (the actual number
58       depends on the key size).
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60       Because key generation is a random process the time taken to generate a
61       key may vary somewhat.
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BUGS

64       A quirk of the prime generation algorithm is that it cannot generate
65       small primes. Therefore the number of bits should not be less that 64.
66       For typical private keys this will not matter because for security
67       reasons they will be much larger (typically 1024 bits).
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SEE ALSO

70       gendsa(1)
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741.0.0e                            2009-04-10                         GENRSA(1)