For this challenge, we are given the following string:
egkyGGJ{Q3e_Xf_FshH3wf}

The string looks like the correct length for the flag. We know the flag format is riftCTF{ so we can eliminate caesar cipher because C and T both encrypted to G. The hint tells us that it is a cipher with a key. The most obvious cipher with a key is vigenere.

Now that we know it is vigenere, we need to figure out the key. The hint also includes a link to Louis Nyffenegger's LinkedIn page. The shortened url is http://bit.ly/l4stnam3 so the key is probably Louis' last name, Nyffenegger.

We decode the vigenere and we find the flag.

Flag: riftCTF{K3y_To_SucC3ss}

Original writeup (https://github.com/joeyjon123/riftCTF/wiki/Crypto-0x002).