CODEWITHSUNDEEP
crypto++
Luciano Santos
Luciano Santos

Reputation: 77

Use ECDH key with ECIES

In Crypto++, I'm trying to use a public key generated by ECDH to encrypt a message with ECIES. Is that possible? The key is stored in a SecByteBlock. I've tried two options: 1) reading the bytes directly via StringSource; 2) creating an Integer and encoding it to BER, then trying to decode it in the public key. None of these options worked, both generate a BER format exception.

What might I be doing wrong? Is there any other way to set the ECIES encryptor public key's bytes directly?

Thanks!

Upvotes: 0

Views: 647

Answers (1)

Luciano Santos
Luciano Santos

Reputation: 77

For anyone wondering, what I was actually trying to do was this... Suppose that at some point a key pair was generated in the following way:

ECDH<ECP>::Domain domain(some_curve);
SecByteBlock prv(domain.PrivateKeyLength()), pub(domain.PublicKeyLength());
domain.GenerateKeyPair(AutoSeededRandomPool(), prv, pub);

Later, given just the raw (bytes) representation, if you need to load these keys for encryption, you could do:

auto& params = domain.GetGroupParameters();
ECIES<ECP>::PrivateKey prv_key;
ECIES<ECP>::PublicKey pub_key;
prv_key.Initialize(params, Integer(prv.begin(), prv.size());
pub_key.Initialize(params, params.DecodeElement(pub, true));

And then create Encryptor/Decryptor as needed:

ECIES<ECP>::Encryptor encptor(pub_key);
ECIES<ECP>::Decryptor decptor(prv_key);

Anyway, thanks for the help in the comments, it put me in the right direction to find the answer!

Upvotes: 2

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