`S1JZUFRPTklTR1JFQVQ=`

frombase64`KRYPTONISGREAT`

- Using CyberChef ðŸŽœ

`YRIRY GJB CNFFJBEQ EBGGRA`

- ROT13 decodes to:
`LEVEL TWO PASSWORD ROTTEN`

- Using CyberChef ðŸŽœ

- Ciphertext:
`OMQEMDUEQMEK`

- Using a Caesar Cipher Breaker we get ROT12 and the Password
`CAESARISEASY`

- Ciphertext:
`KSVVW BGSJD SVSIS VXBMN YQUUK BNWCU ANMJS`

- By pasting all three
`found`

texts and the ciphertext into quipqiup we get an entropy of 1.324 and the Password`BRUTE`

- Ciphertext:
`HCIKV RJOX`

- By pasting all
`found`

texts and the ciphertext into this solving tool we get the vignere key`frekey`

- The password is
`CLEARTEXT`

- ciphertext:
`BELOS Z`

- By pasting all
`found`

texts and the ciphertext into this solving tool we get the vignere key`keylength`

- The Password is
`RANDOM`

- Ciphertext:
`PNUKLYLWRQKGKBE`

- When decompiling the encryption binary, the following expression can be found which is applied to each character:
`random_number + password[password_pos] + upper_plain_char - 'A'`

- The
`random_number`

is not really random, but rather the same each run and repeating - Thus by passing
`AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA`

to the encryption program, we essentially get`random + password + 'A' - 'A'`

- The string output repeats
`EICTDGYIYZKTHNSIRFXYCPFUEOCKRN`

- This string is already the vignere key of the encryption
- Thus we can use CyberChef ðŸŽœ to obtain the password
- The password is
`LFSRISNOTRANDOM`