Example of Passbase metadata encryption in Kotlin

CryptoLogic.kt

class CryptoLogic {
    companion object {
        const val metadataCipher = "RSA/None/PKCS1Padding"
    }

    fun <R> encryptMetadata(plaintext: String, callback: (String) -> R): R {
        return withPublicKey(/* key info... */) { publicKey ->
            // initialize the cipher with the resolved public key
            val cipher: Cipher = Cipher.getInstance(metadataCipher)
            cipher.init(Cipher.ENCRYPT_MODE, publicKey)

            // invoke the callback, after base64-encoding the encrypted output
            callback.invoke(Base64.getEncoder().encodeToString(
                cipher.doFinal(plaintext.toByteArray(StandardCharsets.UTF_8))
            ))
        }
    }

    fun <I, R> encryptMetadataJSON(pojo: I, callback: (String) -> R): R {
        return encryptMetadata(
            objectMapper().writeValueAsString(pojo),
            callback
        )
    }
}