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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | LINKING | SEE ALSO | COLOPHON |
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KEYCTL_DH_COMPUTE(3) Linux Key Management Calls KEYCTL_DH_COMPUTE(3)
keyctl_dh_compute - Compute a Diffie-Hellman shared secret or
public key
keyctl_dh_compute_kdf - Derive key from a Diffie-Hellman shared
secret
#include <keyutils.h>
long keyctl_dh_compute(key_serial_t private, key_serial_t prime,
key_serial_t base, char *buffer, size_t buflen);
long keyctl_dh_compute_alloc(key_serial_t private,
key_serial_t prime, key_serial_t base, void **_buffer);
long keyctl_dh_compute_kdf(key_serial_t private, key_serial_t prime,
key_serial_t base, char *hashname, char *otherinfo,
size_t otherinfolen, char *buffer, size_t buflen);
keyctl_dh_compute() computes a Diffie-Hellman public key or
shared secret. That computation is:
base ^ private ( mod prime )
When base is a key containing the shared generator value, the
remote public key is computed. When base is a key containing the
remote public key, the shared secret is computed.
base, private, and prime must all refer to user-type keys
containing the parameters for the computation. Each of these
keys must grant the caller read permission in order for them to
be used.
buffer and buflen specify the buffer into which the computed
result will be placed. buflen may be zero, in which case the
buffer is not used and the minimum buffer length is fetched.
keyctl_dh_compute_alloc() is similar to keyctl_dh_compute()
except that it allocates a buffer big enough to hold the payload
data and places the data in it. If successful, a pointer to the
buffer is placed in *_buffer. The caller must free the buffer.
keyctl_dh_compute_kdf() derives a key from a Diffie-Hellman
shared secret according to the protocol specified in SP800-56A.
The Diffie-Hellman computation is based on the same primitives as
discussed for keyctl_dh_compute().
To implement the protocol of SP800-56A base is a key containing
the remote public key to compute the Diffie-Hellman shared
secret. That shared secret is post-processed with a key
derivation function.
The hashname specifies the Linux kernel crypto API name for a
hash that shall be used for the key derivation function, such as
sha256. The hashname must be a NULL terminated string. See
/proc/crypto for available hashes on the system.
Following the specification of SP800-56A section 5.8.1.2 the
otherinfo parameter may be provided. The format of the OtherInfo
field is defined by the caller. The caller may also specify NULL
as a valid argument when no OtherInfo data shall be processed.
The length of the otherinfo parameter is specified with
otherinfolen and is restricted to a maximum length by the kernel.
The KDF returns the requested number of bytes specified with the
genlen or the buflen parameter depending on the invoked function.
buffer and buflen specify the buffer into which the computed
result will be placed.
On success keyctl_dh_compute() returns the amount of data placed
into the buffer when buflen is non-zero. When buflen is zero,
the minimum buffer length to hold the data is returned.
On success keyctl_dh_compute_alloc() returns the amount of data
in the buffer.
On error, both functions set errno to an appropriate code and
return the value -1.
ENOKEY One of the keys specified is invalid or not readable.
EINVAL The buffer pointer is invalid or buflen is too small.
EOPNOTSUPP
One of the keys was not a valid user key.
EMSGSIZE
When using keyctl_dh_compute_kdf(), the size of either
otherinfolen or buflen is too big.
This is a library function that can be found in libkeyutils.
When linking, -lkeyutils should be specified to the linker.
keyctl(1),
keyctl(2),
keyctl(3),
keyutils(7)
This page is part of the keyutils (key management utilities)
project. Information about the project can be found at [unknown
-- if you know, please contact man-pages@man7.org] If you have a
bug report for this manual page, send it to
keyrings@linux-nfs.org. This page was obtained from the
project's upstream Git repository
⟨http://git.kernel.org/pub/scm/linux/kernel/git/dhowells/keyutils.git⟩
on 2024-06-14. (At that time, the date of the most recent commit
that was found in the repository was 2023-03-20.) If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better or more up-to-date source for
the page, or you have corrections or improvements to the
information in this COLOPHON (which is not part of the original
manual page), send a mail to man-pages@man7.org
Linux 07 Apr 2016 KEYCTL_DH_COMPUTE(3)
Pages that refer to this page: keyctl(2), keyctl(3)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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