Decrypt given data previously encoded with 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 decryption process assumes the IV string is prepended in the encoded string during the encryption process. You can not decrypt and get the correct results if the IV or passphrase mismatch occurs between encryption and decryption process.