Byte-Integer Encoding (bytes_to_long - long_to_bytes)

Updated 13 Sep 2026

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What it is
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  The convention of treating a byte string as one large big-endian base-256 integer — concatenate each byte's value and read the result as a single number (commonly shown in hex or decimal). This is how message bytes get turned into the integers that RSA, Diffie-Hellman, and other numeric cryptosystems actually operate on.
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When to apply
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  A challenge hands you a huge integer and expects text back, or vice versa — especially anything RSA-flavored, where plaintexts/ciphertexts are always integers under the hood.
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Worked example
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  "HELLO" → ASCII bytes [72, 69, 76, 76, 79] → hex 0x48454c4c4f → decimal 310400273487.

Python

from Crypto.Util.number import bytes_to_long, long_to_bytes
n = bytes_to_long(b"HELLO")     # 310400273487
b = long_to_bytes(n)            # b'HELLO'