50 lines
1.4 KiB
TypeScript
50 lines
1.4 KiB
TypeScript
export type PlaintextBlock = number[][]
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export const preprocessPlaintext = (plaintext: string): PlaintextBlock[] => {
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/**
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* @param {string} plaintext - The plaintext to encrypt.
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* @returns {PlaintextBlock[]} Blocks of 128 bits representing the plaintext. Each block is a 4x4 column-major matrix.
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*/
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const encoder = new TextEncoder()
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const byteArray = encoder.encode(plaintext) // Array where each item is an 8-bit representation of a character of the string
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const blockSize = 16 // 128 bits = 16 bytes
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// Loop through the byteArray and split it into 128-bit blocks
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const blocks: Uint8Array[] = []
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for (let i = 0;i < byteArray.length;i += blockSize) {
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const block = byteArray.slice(i, i + blockSize)
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if (block.length < blockSize) {
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// Pad the block with zeroes
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const paddedBlock = new Uint8Array(blockSize)
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paddedBlock.set(block)
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blocks.push(paddedBlock)
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} else {
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blocks.push(block)
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}
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}
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const plaintextBlocks: number[][][] = blocks.map(block => {
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// Block is a 128-bit array containing 16 8-bit integers.
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const matrix: number[][] = [
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[0, 0, 0, 0],
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[0, 0, 0, 0],
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[0, 0, 0, 0],
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[0, 0, 0, 0],
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]
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// Fill the matrix in column-major order, i.e., top-to-bottom + left-to-right
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for (let i = 0;i < blockSize;i++) {
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const row = i % 4
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const col = Math.floor(i / 4)
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matrix[row][col] = block[i]
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}
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return matrix
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})
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return plaintextBlocks
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}
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