ibm-information-center/dist/eclipse/plugins/i5OS.ic.apis_5.4.0.1/qc3calds.htm

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<title>Calculate Diffie-Hellman Secret Key (QC3CALDS, Qc3CalculateDHSecretKey)</title>
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<h2>Calculate Diffie-Hellman Secret Key (QC3CALDS, Qc3CalculateDHSecretKey)</h2>
<div class="box" style="width: 80%;">
<br>
&nbsp;&nbsp;Required Parameter Group:<br>
<!-- iddvc RMBR -->
<br>
<table width="100%">
<tr>
<td align="center" valign="top" width="10%">1</td>
<td align="left" valign="top" width="60%">D-H algorithm context token</td>
<td align="left" valign="top" width="15%">Input</td>
<td align="left" valign="top" width="15%">Char(8)</td>
</tr>
<tr>
<td align="center" valign="top" width="10%">2</td>
<td align="left" valign="top" width="60%">D-H public key</td>
<td align="left" valign="top" width="15%">Input</td>
<td align="left" valign="top" width="15%">Char(*)</td>
</tr>
<tr>
<td align="center" valign="top" width="10%">3</td>
<td align="left" valign="top" width="60%">Length of D-H public key</td>
<td align="left" valign="top" width="15%">Input</td>
<td align="left" valign="top" width="15%">Binary(4)</td>
</tr>
<tr>
<td align="center" valign="top" width="10%">4</td>
<td align="left" valign="top" width="60%">D-H secret key</td>
<td align="left" valign="top" width="15%">Output</td>
<td align="left" valign="top" width="15%">Char(*)</td>
</tr>
<tr>
<td align="center" valign="top" width="10%">5</td>
<td align="left" valign="top" width="60%">Length of area provided for D-H
secret key</td>
<td align="left" valign="top" width="15%">Input</td>
<td align="left" valign="top" width="15%">Binary(4)</td>
</tr>
<tr>
<td align="center" valign="top" width="10%">6</td>
<td align="left" valign="top" width="60%">Length of D-H secret key
returned</td>
<td align="left" valign="top" width="15%">Output</td>
<td align="left" valign="top" width="15%">Binary(4)</td>
</tr>
<tr>
<td align="center" valign="top" width="10%">7</td>
<td align="left" valign="top" width="60%">Error code</td>
<td align="left" valign="top" width="15%">I/O</td>
<td align="left" valign="top" width="15%">Char(*)</td>
</tr>
</table>
<br>
&nbsp;&nbsp;Service Program Name: QC3DH<br>
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<br>
&nbsp;&nbsp;Default Public Authority: *USE<br>
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<br>
&nbsp;&nbsp;Threadsafe: Yes<br>
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<br>
</div>
<p>Diffie-Hellman (D-H) is a public key algorithm used for producing a shared
secret key. It is described in RFC 2631 and Public Key Cryptography Standard
(PKCS) #3. To share a secret key between two
parties, both parties calculate the shared secret key using their own private
key and the other party's public key. To share a secret key with more than two
parties, see the example below.</p>
<p>Information on cryptographic standards can be found in the <a href=
"qc3crtax.htm">Create Algorithm Context (OPM, QC3CRTAX; ILE,
Qc3CreateAlgorithmContext)</a> API documentation.</p>
<br>
<h3>Authorities and Locks</h3>
<dl>
<dt><strong>Required API authority</strong></dt>
<dd>*USE<br>
<br>
</dd>
<dt><strong>Required device description authority</strong></dt>
<dd>*USE<br>
<br>
</dd>
</dl>
<br>
<h3>Required Parameter Group</h3>
<dl>
<dt><strong>D-H algorithm context token</strong><br>
</dt>
<dd>INPUT; CHAR(8)
<p>The token for the D-H algorithm context.<br>
This must be the token for the algorithm context that was created using the <a href=
"qc3gendk.htm">Generate Diffie-Hellman Key Pair (OPM, QC3GENDK; ILE,
Qc3GenDHKeyPair) API</a>. The D-H parameters and private key are contained in
the context. Once the D-H secret key has been calculated, you should destroy
the D-H algorithm context using the <a href="qc3desax.htm">Destroy Algorithm
Context (OPM, QC3DESAX; ILE, Qc3DestroyAlgorithmContext) API</a>.</p>
</dd>
<dt><strong>D-H public key</strong></dt>
<dd>INPUT; CHAR(*)
<p>The other party's D-H public key.<br>
This is the public key from the party with whom the secret key will be
shared</p>
</dd>
<dt><strong>Length of D-H public key</strong></dt>
<dd>INPUT; BINARY(4)
<p>The length of key specified in the D-H public key parameter.</p>
</dd>
<dt><strong>D-H secret key</strong></dt>
<dd>OUTPUT; CHAR(*)
<p>The area to store the D-H secret key.<br>
The entire output of the secret key may not be needed and the two parties must
agree on which bytes of the secret value will be used.</p>
</dd>
<dt><strong>Length of area provided for D-H secret key</strong></dt>
<dd>INPUT; BINARY(4)
<p>The length of the D-H secret key parameter in bytes.<br>
The size of the secret key will be no greater than the key size. (See <a href=
"qc3gendp.htm">Generate Diffie-Hellman Parameters (OPM, QC3GENDP; ILE,
Qc3GenDHParms) API</a>.) Because key size is normally specified in bits,
divide that value by 8 and round up to obtain the length of area needed for the
D-H secret key.</p>
</dd>
<dt><strong>Length of D-H secret key returned</strong></dt>
<dd>OUTPUT; BINARY(4)
<p>The length of the D-H secret key returned in the D-H secret key
parameter.<br>
If the length of area provided is too small, an error will be generated and no
data will be returned in the D-H secret key parameter.</p>
</dd>
<dt><strong>Error code</strong></dt>
<dd>I/O; CHAR(*)
<p>The structure in which to return error information.<br>
For the format of the structure, see <a href="../apiref/error.htm#hdrerrcod">Error Code
Parameter</a>.</p>
</dd>
</dl>
<br>
<h3><a name="header_9">Error Messages</a></h3>
<table cellpadding="5">
<tr>
<th align="left" valign="top">Message ID</th>
<th align="left" valign="top">Error Message Text</th>
</tr>
<tr>
<td valign="top" width="15%">CPF24B4 E</td>
<td valign="top" width="85%">Severe error while addressing parameter list.</td>
</tr>
<tr>
<td valign="top">CPF3C1E E</td>
<td valign="top">Required parameter &amp;1 omitted.</td>
</tr>
<tr>
<td valign="top">CPF3CF1 E</td>
<td valign="top">Error code parameter not valid.</td>
</tr>
<tr>
<td valign="top">CPF3CF2 E</td>
<td valign="top">Error(s) occurred during running of &amp;1 API.</td>
</tr>
<tr>
<td valign="top">CPF9872 E</td>
<td valign="top">Program or service program &amp;1 in library &amp;2 ended. Reason code &amp;3.</td>
</tr>
<tr>
<td valign="top">CPF9DCA E</td>
<td valign="top">Length of D-H (Diffie-Hellman) public key not valid.</td>
</tr>
<tr>
<td valign="top">CPF9DD6 E</td>
<td valign="top">Length of area provided for output data is too small.</td>
</tr>
<tr>
<td valign="top">CPF9DDA E</td>
<td valign="top">Unexpected return code &amp;1.</td>
</tr>
<tr>
<td valign="top">CPF9DF1 E</td>
<td valign="top">The algorithm context token does not reference a valid algorithm context.</td>
</tr>
<tr>
<td valign="top">CPF9DF2 E</td>
<td valign="top">The algorithm context is not found or was previously destroyed.</td>
</tr>
</table>
<br>
<h3><a name="header_10">Example of Three-Party Shared Secret Key
Exchange</a></h3>
<ol>
<li>Beth uses Generate Diffie-Hellman Parameters and sends the output to Kathy
and Terry.</li>
<li>Beth uses Generate Diffie-Hellman Key Pair to generate a private value
(stored in a Diffie-Hellman algorithm context), and a public value B1, which
she sends to Kathy.</li>
<li>Kathy uses Generate Diffie-Hellman Key Pair to generate a private value
(stored in a Diffie-Hellman algorithm context), and a public value K1, which
she sends to Terry.</li>
<li>Terry uses Generate Diffie-Hellman Key Pair to generate a private value
(stored in a Diffie-Hellman algorithm context), and a public value T1, which he
sends to Beth.</li>
<li>Beth specifies T1 on Calculate Diffie-Hellman Secret Key to create another
public value B2, which she sends to Kathy.</li>
<li>Kathy specifies B1 on Calculate Diffie-Hellman Secret Key to create another
public value K2, which she sends to Terry.</li>
<li>Terry specifies K1 on Calculate Diffie-Hellman Secret Key to create another
public value T2, which he sends to Beth.</li>
<li>Beth specifies T2 on Calculate Diffie-Hellman Secret Key to create the
shared secret key, S.</li>
<li>Kathy specifies B2 on Calculate Diffie-Hellman Secret Key to create the
shared secret key, S.</li>
<li>Terry specifies K2 on Calculate Diffie-Hellman Secret Key to create the
shared secret key, S.</li>
</ol>
<br>
<hr>
API introduced: V5R3
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