TPMCmd/tpm/src/command/Asymmetric/EC_Ephemeral.c

/* Microsoft Reference Implementation for TPM 2.0
 *
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 *  included below. This software may be subject to other third party and
 *  contributor rights, including patent rights, and no such rights are granted
 *  under this license.
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 *  Copyright (c) Microsoft Corporation
 *
 *  All rights reserved.
 *
 *  BSD License
 *
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 *  are permitted provided that the following conditions are met:
 *
 *  Redistributions of source code must retain the above copyright notice, this list
 *  of conditions and the following disclaimer.
 *
 *  Redistributions in binary form must reproduce the above copyright notice, this
 *  list of conditions and the following disclaimer in the documentation and/or
 *  other materials provided with the distribution.
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 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ""AS IS""
 *  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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 */
#include "Tpm.h"
#include "EC_Ephemeral_fp.h"

#if CC_EC_Ephemeral  // Conditional expansion of this file

/*(See part 3 specification)
// This command creates an ephemeral key using the commit mechanism
*/
//  Return Type: TPM_RC
// TPM_RC_NO_RESULT             the TPM is not able to generate an 'r' value
TPM_RC
TPM2_EC_Ephemeral(
    EC_Ephemeral_In     *in,            // IN: input parameter list
    EC_Ephemeral_Out    *out            // OUT: output parameter list
    )
{
    TPM2B_ECC_PARAMETER      r;
    TPM_RC                   result;
//
    do
    {
        // Get the random value that will be used in the point multiplications
        // Note: this does not commit the count.
        if(!CryptGenerateR(&r, NULL, in->curveID, NULL))
            return TPM_RC_NO_RESULT;
        // do a point multiply
        result = CryptEccPointMultiply(&out->Q.point, in->curveID, NULL, &r,
                                       NULL, NULL);
        // commit the count value if either the r value results in the point at
        // infinity or if the value is good. The commit on the r value for infinity
        // is so that the r value will be skipped.
        if((result == TPM_RC_SUCCESS) || (result == TPM_RC_NO_RESULT))
            out->counter = CryptCommit();
    } while(result == TPM_RC_NO_RESULT);

    return TPM_RC_SUCCESS;
}

#endif // CC_EC_Ephemeral