The given string is:
```RFVDVEZ7MTZfaDBtM19ydW41X20zNG41X3J1bm4xbjZfcDQ1N182NF9iNDUzNX0=```
With the equals sign at the end, the string is a pretty dead giveaway for Base 64 encryption. Running it through a decryptor we get the flag.
**Flag**: `DUCTF{16_h0m3_run5_m34n5_runn1n6_p457_64_b4535}`  **Tools**: [Base64 decoder](https://gchq.github.io/CyberChef/#recipe=From_Base64('A-Za-z0-9%2B/%3D',true))