Encrypt given data using sm4-cfb cipher algo. SM4 in CFB (Cipher Feedback) mode, using feedback to convert the block cipher into a stream cipher. CFB mode was added to SM4 to handle data streams securely while ensuring high performance. SM4-CFB is secure and well-suited for applications that require stream cipher functionality. Our encryption process prepends the IV string used during the encryption process in the encrypted data so that it can be used during decryption.