Decrypt given data previously encoded with sm4-ofb cipher algo. SM4 in OFB (Output Feedback) mode, using feedback to turn the block cipher into a stream cipher. OFB mode is used with SM4 for efficient stream encryption, though it is less commonly used than other modes like CTR. SM4-OFB is secure, but newer modes like CTR are generally preferred for modern cryptographic applications. 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.