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<p class="MsoNormal"><b>From:</b> Narayana, Sunil Kumar <sanarayana@rbbn.com> <br>
<b>Sent:</b> Thursday, December 17, 2020 8:17 AM<br>
<b>To:</b> Sands, Daniel <dnsands@sandia.gov>; openssl-users@openssl.org<br>
<b>Subject:</b> [EXTERNAL] RE: DH_compute_key () - replacement in 3.0<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span lang="EN-IN">Hi,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN"> For the equivalent replacement of DH_compute_key in 3.0, we tried to perform the steps suggested in earlier mail below<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN">Our steps are as follows, but we see EVP_PKEY_derive fails to perform. please suggest if any steps are wrong or missing here.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN"> <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN">//input - BIGNUM - pubkey, privkey, p ,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN">//output - sharedsecret<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN"> <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN">Evp_compute_key(unsigned char* sharedSecret, unsigned int len, BIGNUM *pubkey, BIGNUM *privkey, BIGNUM* dh_p)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN">{<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN">OSSL_PARAM params[5];<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN">unsigned char* p_str = BN_bn2dec (dh_p);<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN">unsigned char* pub_str = BN_bn2dec (pubkey);<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN">unsigned char* priv_str = BN_bn2dec (privkey);<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN"> <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN">params[0] = OSSL_PARAM_construct_BN(OSSL_PKEY_PARAM_FFC_P, p_str, strlen(p_str));<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN">params[1] = OSSL_PARAM_construct_uint(OSSL_PKEY_PARAM_FFC_G, &g);<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN">params[2] = OSSL_PARAM_construct_BN(OSSL_PKEY_PARAM_PUB_KEY, pub_str, strlen(pub_str));<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN">params[3] = OSSL_PARAM_construct_BN(OSSL_PKEY_PARAM_PRIV_KEY, priv_str, strlen(priv_str));<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN">params[4] = OSSL_PARAM_construct_end();<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN"> <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN">gctx = EVP_PKEY_CTX_new_from_name(NULL, "DH", NULL);<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN">EVP_PKEY_derive_init(gctx)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN">EVP_PKEY_CTX_set_params(gctx, params)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN"> <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN">/* Determine buffer length */<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN">EVP_PKEY_derive(gctx, NULL, &skeylen)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN">EVP_PKEY_derive(gctx, sharedSecret, &skeylen)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN">}<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN"> <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN">Note - EVP_PKEY_derive -- call fails what is wrong in the steps can you please g<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN">To derive a shared secret, you also need your peer’s public key. It will also be presented as an EVP_PKEY structure.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-IN"> </span><span lang="EN-IN" style="font-size:8.0pt;font-family:"Arial",sans-serif"><o:p></o:p></span></p>
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