useful functions

These are the uses of functions:

• encryptMessage(publicKey,msg,Uint8Array(16) IV)) encrypt string msg with AES-CBC key publicKey and the local IV. Returns a string containing the "ciphertext".
• decryptMessage(publicKey,msg,Uint8Array(16) IV)) decrypt string msg with AES-CBC key publicKey and the local IV. Returns a string containing the "plaintext".