Encrypt given data using des-cfb1 cipher algo. DES in CFB1 mode, encrypting 1 bit at a time using feedback from previous ciphertext blocks. Introduced as part of the DES modes to allow for encryption of smaller data units. DES-CFB1 is secure within the context of older systems, but DES itself is now obsolete due to vulnerabilities in its key length. Our encryption process prepends the IV string used during the encryption process in the encrypted data so that it can be used during decryption.