Need to cleanup sensitive key data after using

[Liu Wei]

vtpm-td/src/tpm/src/tpm2_ca_cert.rs

Line 46 in abf493e

 let pkcs8 = generate_ecdsa_keypairs(); 

vtpm-td/src/tpm/src/tpm2_ca_cert.rs

Lines 53 to 56 in abf493e

 let key_pair = EcdsaKeyPair::from_pkcs8( 
     &ring::signature::ECDSA_P384_SHA384_ASN1_SIGNING, 
     pkcs8.as_ref(), 
 ); 

vtpm-td/src/tpm/src/tpm2_provision.rs

Lines 515 to 521 in abf493e

 let key_pair = ring::signature::EcdsaKeyPair::from_pkcs8( 
     &signature::ECDSA_P384_SHA384_ASN1_SIGNING, 
     pkcs8.as_slice(), 
 ); 
 if key_pair.is_err() { 
     break; 
 }