1KEYCTL_DH_COMPUTE(3)      Linux Key Management Calls      KEYCTL_DH_COMPUTE(3)
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NAME

6       keyctl_dh_compute  -  Compute  a Diffie-Hellman shared secret or public
7       key
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SYNOPSIS

10       #include <keyutils.h>
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12       long keyctl_dh_compute(key_serial_t private, key_serial_t prime,
13       key_serial_t base, char *buffer, size_t buflen);
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15       long keyctl_dh_compute_alloc(key_serial_t private,
16       key_serial_t prime, key_serial_t base, void **_buffer);
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DESCRIPTION

19       keyctl_dh_compute() computes a  Diffie-Hellman  public  key  or  shared
20       secret.  That computation is:
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22              base ^ private ( mod prime )
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24       When  base  is  a key containing the shared generator value, the remote
25       public key is computed.  When base is a key containing the remote  pub‐
26       lic key, the shared secret is computed.
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28       base,  private,  and  prime must all refer to user-type keys containing
29       the parameters for the computation.  Each of these keys must grant  the
30       caller read permission in order for them to be used.
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32       buffer  and  buflen  specify  the buffer into which the computed result
33       will be placed.  buflen may be zero, in which case the  buffer  is  not
34       used and the minimum buffer length is fetched.
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36       keyctl_dh_compute_alloc() is similar to keyctl_dh_compute() except that
37       it allocates a buffer big enough to hold the payload  data  and  places
38       the  data  in  it.  If successful, a pointer to the buffer is placed in
39       *_buffer.  The caller must free the buffer.
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RETURN VALUE

42       On success keyctl_dh_compute() returns the amount of data  placed  into
43       the  buffer  when buflen is non-zero.  When buflen is zero, the minimum
44       buffer length to hold the data is returned.
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46       On success keyctl_dh_compute_alloc() returns the amount of data in  the
47       buffer.
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49       On  error,  both  functions set errno to an appropriate code and return
50       the value -1.
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ERRORS

53       ENOKEY One of the keys specified is invalid or not readable.
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55       EINVAL The buffer pointer is invalid or buflen is too small.
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57       EOPNOTSUPP
58              One of the keys was not a valid user key.
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LINKING

61       This is a library function that can  be  found  in  libkeyutils.   When
62       linking, -lkeyutils should be specified to the linker.
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SEE ALSO

65       keyctl(1),
66       keyctl(2),
67       keyctl(3),
68       keyutils(7)
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72Linux                             07 Apr 2016             KEYCTL_DH_COMPUTE(3)
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