package org.bouncycastle.pqc.crypto.cmce;

import java.security.SecureRandom;

import org.bouncycastle.crypto.EncapsulatedSecretGenerator;
import org.bouncycastle.crypto.SecretWithEncapsulation;
import org.bouncycastle.crypto.params.AsymmetricKeyParameter;
import org.bouncycastle.pqc.crypto.util.SecretWithEncapsulationImpl;

/**
 * @deprecated the standardised Classic McEliece KEM (ISO/IEC 18033-2:2006/Amd 2:2026) is now provided under org.bouncycastle.crypto and org.bouncycastle.jcajce (see org.bouncycastle.crypto.params.CMCEParameters and org.bouncycastle.jcajce.spec.CMCEParameterSpec). This is the legacy NIST round 3 (non-pc, incl. mceliece348864) implementation, retained for backwards compatibility.
 */
@Deprecated
public class CMCEKEMGenerator
    implements EncapsulatedSecretGenerator
{
    // the source of randomness
    private final SecureRandom sr;

    public CMCEKEMGenerator(SecureRandom random)
    {
        this.sr = random;
    }

    public SecretWithEncapsulation generateEncapsulated(AsymmetricKeyParameter recipientKey)
    {
        CMCEPublicKeyParameters key = (CMCEPublicKeyParameters)recipientKey;
        CMCEEngine engine = key.getParameters().getEngine();

        return generateEncapsulated(recipientKey, engine.getDefaultSessionKeySize());
    }

    public SecretWithEncapsulation generateEncapsulated(AsymmetricKeyParameter recipientKey, int sessionKeySizeInBits)
    {
        CMCEPublicKeyParameters key = (CMCEPublicKeyParameters)recipientKey;
        CMCEEngine engine = key.getParameters().getEngine();
        byte[] cipher_text = new byte[engine.getCipherTextSize()];
        byte[] sessionKey = new byte[sessionKeySizeInBits / 8];     // document as 32 - l/8  - Section 2.5.2
        engine.kem_enc(cipher_text, sessionKey, key.getPublicKey(), sr);
        return new SecretWithEncapsulationImpl(sessionKey, cipher_text);
    }
}
