KeyPair.kt

KeyPair.kt

private lateinit var keyPair: KeyPair

private fun generateKey() {
    val startDate = GregorianCalendar()
    val endDate = GregorianCalendar()
    endDate.add(Calendar.YEAR, 1)
    
    val keyPairGenerator: KeyPairGenerator = KeyPairGenerator.getInstance(KeyProperties.KEY_ALGORITHM_RSA, ANDROID_KEYSTORE)

    val parameterSpec: KeyGenParameterSpec = KeyGenParameterSpec.Builder(KEY_ALIAS,
        KeyProperties.PURPOSE_SIGN or KeyProperties.PURPOSE_VERIFY).run {
            setCertificateSerialNumber(BigInteger.valueOf(777))       //Serial number used for the self-signed certificate of the generated key pair, default is 1
            setCertificateSubject(X500Principal("CN=$KEY_ALIAS"))     //Subject used for the self-signed certificate of the generated key pair, default is CN=fake
            setDigests(KeyProperties.DIGEST_SHA256)                         //Set of digests algorithms with which the key can be used
            setSignaturePaddings(KeyProperties.SIGNATURE_PADDING_RSA_PKCS1) //Set of padding schemes with which the key can be used when signing/verifying
            setCertificateNotBefore(startDate.time)                         //Start of the validity period for the self-signed certificate of the generated, default Jan 1 1970
            setCertificateNotAfter(endDate.time)                            //End of the validity period for the self-signed certificate of the generated key, default Jan 1 2048
            setUserAuthenticationRequired(true)                             //Sets whether this key is authorized to be used only if the user has been authenticated, default false
            setUserAuthenticationValidityDurationSeconds(30)                //Duration(seconds) for which this key is authorized to be used after the user is successfully authenticated
            build()
    }

    //Initialization of key generator with the parameters we have specified above
    keyPairGenerator.initialize(parameterSpec)

    //Generates the key pair
    keyPair = keyPairGenerator.genKeyPair()
}