I have more than 15 years experience in C, C++, C#, Java, Objective-C, Swift on various platforms like Windows, Linux (various flavors), Mac OSX, iOS, Android, QNX RTOS, etc. In my recent project I have worked on writing some of the standard encryption algorithms like AES, DES, RSA, Blowfish, etc written in C. These are used for providing encryption of data for a SQL Engine. I have also worked on TLS 1.2 and TLS 1.3 used for connection between client and server and which uses encryption to ensure logon can be done without any breach of security.
If you can provide relevant details, then I can provide you a better estimate of the work to be done.
In case I am awarded the project, I will provide you 2 months of free support for a maximum of 80 hours after handover of the project. After that if support or maintenance is needed, that also can be provided at a mutually agreed terms.