import {
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BlockCipherMode,
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} from './cipher-core.js';
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function generateKeystreamAndEncrypt(words, offset, blockSize, cipher) {
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const _words = words;
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let keystream;
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// Shortcut
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const iv = this._iv;
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// Generate keystream
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if (iv) {
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keystream = iv.slice(0);
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// Remove IV for subsequent blocks
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this._iv = undefined;
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} else {
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keystream = this._prevBlock;
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}
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cipher.encryptBlock(keystream, 0);
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// Encrypt
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for (let i = 0; i < blockSize; i += 1) {
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_words[offset + i] ^= keystream[i];
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}
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}
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/**
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* Cipher Feedback block mode.
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*/
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export class CFB extends BlockCipherMode {
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}
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CFB.Encryptor = class extends CFB {
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processBlock(words, offset) {
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// Shortcuts
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const cipher = this._cipher;
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const { blockSize } = cipher;
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generateKeystreamAndEncrypt.call(this, words, offset, blockSize, cipher);
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// Remember this block to use with next block
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this._prevBlock = words.slice(offset, offset + blockSize);
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}
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};
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CFB.Decryptor = class extends CFB {
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processBlock(words, offset) {
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// Shortcuts
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const cipher = this._cipher;
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const { blockSize } = cipher;
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// Remember this block to use with next block
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const thisBlock = words.slice(offset, offset + blockSize);
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generateKeystreamAndEncrypt.call(this, words, offset, blockSize, cipher);
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// This block becomes the previous block
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this._prevBlock = thisBlock;
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}
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};
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