Topic: [SOLVED] How to generate a ECC public key from a certificate?
Hello everyone,
Due to I want to make ECC key agreement with a certificate and a private key. But I do not know how to generate a ECC public key with a certificate? I referred to the discussed thread:Getting public key from certificate, but I cannot find a API like RsaPublicKeyDecode() to get ECC key from a certificate.
In my concept, I will use APIs to run key agreement as followings:
(This is refer to the thread: http://www.yassl.com/forums/topic513-ge … icate.html)
int ret;
int pemCertSz, derKeySz;
byte pemCert[4096];
byte derKey[1024];
byte shSecret[1024];
FILE* pubFile;
FILE* priFile;
ecc_key pubKey, priKey;
word32 idx = 0;
DecodedCert cert;
/* open and read PEM-formatted cert into buffer */
pubFile= fopen("./client-cert.pem", "rb");
if (!pubFile)
// error reading file
pemCertSz = fread(pemCert, 1, sizeof(pemCert), pubFile);
fclose(pubFile);
/* initialize DecodedCert with PEM cert */
InitDecodedCert(&cert, pemCert, pemCertSz, 0);
ret = ParseCert(&cert, CERT_TYPE, NO_VERIFY, 0);
if (ret != 0)
// ParseCert failed
/* extract the public key from the cert */
ecc_init(&pubKey);
idx = 0;
/* I want to use a API like this to get public key from a certificate. However, this API is not existed! */
ret = EccPublicKeyDecode(cert.publicKey, &idx, &pubKey, cert.pubKeySize);
if (ret != 0)
// EccPublicKeyDecode failed
/* Load private key from DER-formatted file */
priFile= fopen("./ecc-key.der", "rb");
if (!priFile)
// error reading file
derKeySz = fread(derKey, 1, sizeof(derKey), priFile);
fclose(priFile);
/* Translate buffer to ECC private key */
ecc_init(&priKey);
idx = 0;
ret = EccPrivateKeyDecode(derKey, &idx, &priKey, derKeySz);
/* run ECC Key Agreement */
idx = sizeof(shSecret);
ret = ecc_shared_secret(&priKey, &pubKey, shSecret, &idx);Could anyone give me a hand for this issue?
windsp