Byte Array XOR Mask Tool

XOR bytes with a nonempty repeating byte mask; this reversible transform is not encryption.

Description

XOR bytes with a nonempty repeating byte mask; this reversible transform is not encryption.

A repeating XOR mask transforms byte positions with a cyclic sequence of mask bytes.

When to use this tool

XOR bytes with a nonempty repeating byte mask; this reversible transform is not encryption.

Prepare the supplied bytes, mask fields for this operation.
Compare the complete example with the representation used by your own input before carrying the result into another step.

How to use the tool and how it works

Enter bytes, mask. Use the exact text syntax, units and index conventions explained below.
Run the tool. If input validation fails, correct the supplied fields before interpreting any result.
Read result.bytes. Interpret false, null and empty lists using the distinctions below; they can be valid outputs.

Require a nonempty byte mask. For each source byte j return byte XOR mask[j modulo mask length].^[1]

Input field	Meaning and representation	Accepted input
bytes	bytes.	List of integers from 0 to 255; at most 128 bytes
mask	mask.	List of integers from 0 to 255; at most 128 bytes

Output field	Interpretation
result	Object containing the named outputs below.
result.bytes	The bytes list in the ordering and representation described above.

json

{
  "input": {
    "bytes": [
      1,
      2,
      3
    ],
    "mask": [
      255,
      0
    ]
  },
  "output": {
    "result": {
      "bytes": [
        254,
        2,
        252
      ]
    }
  }
}

Limitations and assumptions

This reversible transform provides no cryptographic security or authentication. No random key, padding or transport data is generated.
Every declared top-level field is required and unexpected fields are rejected. Numeric inputs must be finite; ordinary text fields are bounded to 8,192 UTF-16 code units, with tighter operation-specific limits where stated.
Lists are limited to 128 entries. JSON text must meet bounded size and depth checks, and numeric outputs beyond the safe finite magnitude are rejected. Exact large integers use decimal strings.
Indexes are zero-based and spans have an exclusive end unless explicitly stated otherwise. A valid false, null or empty-list result is distinct from malformed input.

Alternative or Complementary methods

Retain the field-width, bit-index and byte-order conventions when combining operations. Slicing, escaping, permutation and alignment are separate transforms; none supplies a complete framing or cryptographic protocol.

References

Tool behavior and example: Byte Array XOR Mask Tool — tool.io

Similar or alternative tools

Byte Array Escaping Inverse
Explicit byte-stuffing inverse with escape followed by reserved byte XOR 0x20; escape and sentinel must differ.
Byte Array Escaping Transform
Explicit byte-stuffing transform with escape followed by reserved byte XOR 0x20; escape and sentinel must differ.