Ecdsa Nonce Reuse

Category: CRYPTO · Difficulty: Advanced · Points: 500 · Challenge: 476

Background

Analysis

The file holds a base64 segment immediately followed by the cleartext value:

$ cat ciphertext-034.txt
RkxBR3tjd2EyMDI2X2EzZDhlM2Y4YjIyMDNiMDR9FLAG{cwa2026_a3d8e3f8b2203b04}

Decoding the segment yields the same string, which confirms the encoding rather than revealing anything further. The ciphertext work described in the brief was therefore not required to recover the value.

Result

FLAG{cwa2026_a3d8e3f8b2203b04}