How to use rsa key pair for AES encryption and decryprion in golang

Question

I want to generate RSA key pair(public and private), and then use them for AES encryption and decryption .e.g. Public key for encryption and private key for decryption. I wrote a simple code for this, but the problem is that when I run this code I get this error:

crypto/aes: invalid key size 1639

How can I resolve this problem ?? My encryption code is given below:

//genrating private key
privateKey, err := rsa.GenerateKey(rand.Reader, 2014)
if err != nil {
    return
}
privateKeyDer := x509.MarshalPKCS1PrivateKey(privateKey)
privateKeyBlock := pem.Block{
    Type:    "RSA PRIVATE KEY",
    Headers: nil,
    Bytes:   privateKeyDer,
}
privateKeyPem := string(pem.EncodeToMemory(&privateKeyBlock))

//using privateKeyPem for encryption
text := []byte("My name is Astaxie")
ciphertext, err := encrypt(text, []byte(privateKeyPem))
if err != nil {
    // TODO: Properly handle error
    log.Fatal(err)
}
fmt.Printf("%s => %x\n", text, ciphertext)
    
//Definition of encrypt()
func encrypt(plaintext []byte, key []byte) ([]byte, error) {
    c, err := aes.NewCipher(key)
    if err != nil {
        return nil, err
    }

    gcm, err := cipher.NewGCM(c)
    if err != nil {
        return nil, err
    }

    nonce := make([]byte, gcm.NonceSize())
    if _, err = io.ReadFull(rand.Reader, nonce); err != nil {
        return nil, err
    }

    return gcm.Seal(nonce, nonce, plaintext, nil), nil
}

What is definition of `encrypt()` function? Show us [Minimal, Complete, and Verifiable example](https://stackoverflow.com/help/mcve) — ymonad, Apr 18 '17 at 04:08
@DarkSquirrel42 yes exactly i want to use rsa key in aes ciper. what mistake i am doing ?? — Raja Hammad Farooq, Apr 18 '17 at 11:50
@Fimzy encrypt(text, []byte(privateKeyPem)) this generates an error. — Raja Hammad Farooq, Apr 18 '17 at 11:53
your cipher expects you to provide a specific size byte array holding the key ... for AES-128 that is 128 bit ... for AES-256 that is 256 bit ... etc ... but you don't have such a byte array holding a key ... you have a string holding a pem encoded x509 structure...what you want to google is "hybrid cryptography" — DarkSquirrel42, Apr 18 '17 at 11:55
@DarkSquirrel42 Thanks, I have searched "hybrid cryptography" , Hope this would solve my problem. — Raja Hammad Farooq, Apr 18 '17 at 12:27

score 0 · Accepted Answer · answered Apr 18 '17 at 12:34

0

As suggested in comments, i searched "hybrid cryptography" . And this example has solved my problem.

answered Apr 18 '17 at 12:34

Raja Hammad Farooq

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How to use rsa key pair for AES encryption and decryprion in golang

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