swift进行RSA加解密时，如果使用 OAEP时，有什么区别？

1.RSA加密

     @objc public func encrypt(source: String, padding: SecPadding = SecPadding.PKCS1) -> String {
        
        guard source.count > 0 && self.publicSecKey != nil else {
            return ""
        }
        
        let data: NSData = (source.data(using: String.Encoding.utf8)! as NSData)
        
 /*       if #available(iOS 10.0, *) {
            var error: Unmanaged<CFError>?
            resData =  SecKeyCreateEncryptedData(self.publicSecKey!, SecKeyAlgorithm.rsaEncryptionPKCS1, data as CFData, &error)

            print("res = \(String(describing: error?.takeUnretainedValue().localizedDescription))")
        }
*/
        // Fallback on earlier versions
        let blockLen =  SecKeyGetBlockSize(self.publicSecKey!)
        var outBuf = [UInt8](repeating: 0, count: blockLen)
        var outBufLen:Int = blockLen
        
        var index = 0
        let totalLen = data.length
        
        let resData = NSMutableData()
        
        var blockMaxLen = blockLen
        
        switch padding {
        case SecPadding.PKCS1:
            blockMaxLen = blockLen - 11
            break
        case SecPadding.OAEP:
            blockMaxLen = blockLen - 42
            break
        default:
            print("blockMaxLen == blockLen")
        
            break
        }
        
        while index < totalLen {
            var curDataLen = totalLen - index;
            if curDataLen  > blockMaxLen {
                curDataLen = blockMaxLen;
            }
            
            let curData: NSData = (data.subdata(with: NSMakeRange(index, curDataLen)) as NSData)
            
            let status: OSStatus = SecKeyEncrypt(self.publicSecKey!, SecPadding.OAEP, curData.bytes.assumingMemoryBound(to: UInt8.self), curData.length, &outBuf, &outBufLen)
            
            if status == noErr {
                resData.append(outBuf, length: outBufLen)
            }else{
                print("encrypt status = \(status)")
            }
            
            index += curDataLen
        }
        
        //base64 encode
        return resData.base64EncodedString(options: NSData.Base64EncodingOptions(rawValue: NSData.Base64EncodingOptions.lineLength64Characters.rawValue))
    }
    

2.RSA解密

 @objc public func decrypt(source: String, padding: SecPadding = SecPadding.PKCS1) -> String {
        
        guard source.count > 0 && self.privateSecKey != nil else {
            return ""
        }
        
        //base64 decode
        let data: Data = (NSData(base64Encoded: (source as String), options: NSData.Base64DecodingOptions.ignoreUnknownCharacters)! as Data)
        
        let blockLen =  SecKeyGetBlockSize(self.privateSecKey!)
        let outBuf = UnsafeMutablePointer<UInt8>.allocate(capacity: blockLen)
        defer {
            outBuf.deallocate()
        }
        
        var outBufLen: Int = blockLen
        
//        if #available(iOS 10.0, *) {
//            var error: Unmanaged<CFError>?
//            resData =  SecKeyCreateDecryptedData(self.privateSecKey!, SecKeyAlgorithm.rsaEncryptionPKCS1, data as CFData, &error)
//
//            print("res = \(String(describing: error?.takeUnretainedValue().localizedDescription))")
//        } else {
//            // Fallback on earlier versions
//            //let status = SecKeyEncrypt(seckey, SecPadding.PKCS1, chunkData, chunkData.count, outBuf, &encryptedDataLength)
//
//        }
        

        var index = 0
        let totalLen = data.count
        
        let resData = NSMutableData()
        
        while index < totalLen {
            var curDataLen = totalLen - index;
            if curDataLen  > blockLen {
                curDataLen = blockLen;
            }
            
            let curData: Data = data.subdata(in: index ..< index + curDataLen)
            
            var status:OSStatus = noErr
            curData.withUnsafeBytes { (bytes: UnsafePointer<UInt8>) in
                 status = SecKeyDecrypt(self.privateSecKey!, padding, bytes, curData.count, outBuf, &outBufLen)
            }
            
            if status == noErr {
                resData.append(outBuf, length: outBufLen)
            }else{
                print("decrypt status = \(status)")
            }
            
            index += curDataLen
        }

        return String(data: (resData as Data), encoding: String.Encoding.utf8)!
    }

3.注意事项

• 1.rsa加解密方式要一致，默认是SecPadding.PKCS1模式。
• 2.rsa不同加密模式，会影响数据分块大小。
  • PKCS1模式时：数据块长度最大为块长度-11
  • OAEP模式时，数据块长度最大为块长度-42