The term post-office box is identified in base64 scheme by the sequence cG9zdC1vZmZpY2UgYm94, while the MD5 signature is equal to 15e5e3ef4efd9b34642b30e7a8a8b4df. The ASCII encoding of post-office box in hexadecimal notation is 706f73742d6f666669636520626f78.