This is the Kotlin code:

private fun verify(inputDataToVerify: String, signature: String): Boolean {
    return try {
        val pubKey = "XXXMYPUBKEYXXX"
        val bytesFromPropFile = pubKey.toByteArray()
        val keySpec = X509EncodedKeySpec(Base64.decode(bytesFromPropFile, Base64.DEFAULT))
        val keyFactory = KeyFactory.getInstance("RSA")
        val publicKey = keyFactory.generatePublic(keySpec)
        Signature.getInstance("SHA512WithRSA").run {
            initVerify(publicKey)
            update(inputDataToVerify.toByteArray())
            verify(Base64.decode(signature.toByteArray(), Base64.DEFAULT))
        }
    } catch (ex: Exception) {
        Timber.e(ex)
        false
    }
}

I have to convert this piece of code to Swift because I need the same behavior in my iOS app but I'm really new to encryption. How can I do? I need third part library?

CodePudding user response：

You don't need to encrypt anything, you need to verify a signature. The algorithms are:

• SubjectPublicKeyInfo or spki for the public key (as defined in the X509 certificate standards, hence the name);
• The old RSA / PKCS#1 signature verification algorithm (obviously with SHA-512 as hash algorithm).

Note that toByteArray() encodes a string to binary using UTF-8 as default. Obviously it should not really be needed before base 64 decoding, but yeah...

CodePudding user response：

i found a solution with SwiftyRSA, that's the method

private func verifySignature(inputDataToVerify: String, signature: String) -> Bool{
    
    let pubKeyString = environmentService.getNexiPubKey()
    
    do {
        let publicKey = try PublicKey(pemEncoded: pubKeyString)
        let clear = try ClearMessage(string: inputDataToVerify, using: .utf8)
        let sign = try Signature(base64Encoded: signature)
        let isSuccessfull = try clear.verify(with: publicKey, signature: sign, digestType: .sha512)
        
        return isSuccessfull
    }
    catch let error{
        print(error)
        return false
    }

}