Question

i generated a public/private keypair using java. Since i want to add the key to my code (not as file) i used

byte[] priv = private_key.getEncoded() 

to get it as a byte array.
To get back the private key from the byte array i use

PKCS8EncodedKeySpec privateKeySpec = new PKCS8EncodedKeySpec(priv);

Decryption is working as expected.
But now i want to use that key inside a c application using openssl.
So i copied the byte array from java to c as a char[].
But i’m not able to convert this char[] into a private key to use it for decryption via RSA_public_decrypt(…)
I tried

RSA *r = d2i_RSAPrivateKey(NULL,&priv, len);

but this always return a NULL pointer

Can anyone please give me a hint on how to do this in c language?

Edit: Meanwhile i checked the error code from openssl and it says

error:0D0680A8:lib(13):func(104):reason(168)

But i don’t know whet to do with those error codes. A search on the net didn’t help yet.

Many thanks in advance.
Greetings, -chris-

Answer 1

Thanks to hint from srikanth yaradla i found the right direction.
Here’s how i did it:

const unsigned char private_key[] = {0x30,...};
size_t private_key_len = sizeof(private_key);
char* buf = (char*)malloc(private_key_len);
memcpy(buf, private_key, private_key_len);
BIO* mem=BIO_new_mem_buf(buf, private_key_len);
PKCS8_PRIV_KEY_INFO* p8inf = d2i_PKCS8_PRIV_KEY_INFO_bio(mem, NULL);
EVP_PKEY* pkey = EVP_PKCS82PKEY(p8inf);
RSA* r = EVP_PKEY_get1_RSA(pkey);

after doing that i now can easily decrypt data i get from the java part.