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.IX Title "TPM_IO_Hash_Start 3"
.TH TPM_IO_Hash_Start 3 2026-01-02 libtpms ""
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.nh
.SH NAME
TPM_IO_Hash_Start   \- indicate the beginging of a TPM TIS hash operation
.PP
TPM_IO_Hash_Data    \- hash the provided data
.PP
TPM_IO_Hash_End     \- indicate the end of a TPM TIS hash operation
.SH LIBRARY
.IX Header "LIBRARY"
TPM library (libtpms, \-ltpms)
.SH SYNOPSIS
.IX Header "SYNOPSIS"
\&\fB#include <libtpms/tpm_types.h\fR>
.PP
\&\fB#include <libtpms/tpm_tis.h\fR>
.PP
\&\fB#include <libtpms/tpm_error.h\fR>
.PP
\&\fBTPM_RESULT TPM_IO_Hash_Start(void);\fR
.PP
\&\fBTPM_RESULT TPM_IO_Hash_Data(const unsigned char\fR *\fIdata\fR\fB,
                            uint32_t\fR \fIdata_length\fR\fB);\fR
.PP
\&\fBTPM_RESULT TPM_IO_Hash_End(void);\fR
.SH DESCRIPTION
.IX Header "DESCRIPTION"
The \fBTPM_IO_Hash_Start()\fR function can be used by an implementation of the
TPM TIS hardware interface to indicate the beginning of a hash operation.
Following the TPM TIS interface specification it resets several PCRs and
terminates existing transport sessions. 
The \fBTPM_IO_Hash_Data()\fR function is used to send the data to be hashed to
the TPM.
The \fBTPM_IO_Hash_End()\fR function calculates the final hash and stores it
in the locality 4 PCR.
The 3 functions must be called in the order they were explained.
.PP
The implementation of the above functions handles all TPM\-internal actions
such as the setting and clearing of permanent flags and PCRs and the
calculation of the hash. Any functionality related to the TPM\*(Aqs TIS interface
and the handling of flags, locality and state has to be implemented by the
caller.
.SH ERRORS
.IX Header "ERRORS"
.IP \fBTPM_SUCCESS\fR 4
.IX Item "TPM_SUCCESS"
The function completed successfully.
.IP \fBTPM_FAIL\fR 4
.IX Item "TPM_FAIL"
General failure.
.IP \fBTPM_INVALID_POSTINIT\fR 4
.IX Item "TPM_INVALID_POSTINIT"
The \fBTPM_IO_Hash_Start()\fR function was called before the TPM received
a TPM_Startup command.
.IP \fBTPM_SHA_THREAD\fR 4
.IX Item "TPM_SHA_THREAD"
The \fBTPM_IO_Hash_Data()\fR or \fBTPM_IO_Hash_End()\fR functions were called before
the \fBTPM_IO_Hash_Start()\fR function.
.PP
For a complete list of TPM error codes please consult the include file
\&\fBlibtpms/tpm_error.h\fR
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBTPMLIB_MainInit\fR(3), \fBTPMLIB_Terminate\fR(3), \fBTPMLIB_RegisterCallbacks\fR(3),
\&\fBTPMLIB_Process\fR(3)