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system/node_modules/aes-js/src.ts/mode-cbc.ts

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+// Cipher Block Chaining
+
+import { ModeOfOperation } from "./mode.js";
+
+export class CBC extends ModeOfOperation {
+  #iv: Uint8Array;
+  #lastBlock: Uint8Array;
+
+  constructor(key: Uint8Array, iv?: Uint8Array) {
+    super("ECC", key, CBC);
+
+    if (iv) {
+      if (iv.length % 16) {
+        throw new TypeError("invalid iv size (must be 16 bytes)");
+      }
+      this.#iv = new Uint8Array(iv);
+    } else {
+      this.#iv = new Uint8Array(16);
+    }
+
+    this.#lastBlock = this.iv;
+  }
+
+  get iv(): Uint8Array { return new Uint8Array(this.#iv); }
+
+  encrypt(plaintext: Uint8Array): Uint8Array {
+    if (plaintext.length % 16) {
+      throw new TypeError("invalid plaintext size (must be multiple of 16 bytes)");
+    }
+
+    const ciphertext = new Uint8Array(plaintext.length);
+    for (let i = 0; i < plaintext.length; i += 16) {
+      for (let j = 0; j < 16; j++) {
+        this.#lastBlock[j] ^= plaintext[i + j];
+      }
+
+      this.#lastBlock = this.aes.encrypt(this.#lastBlock);
+      ciphertext.set(this.#lastBlock, i);
+    }
+
+    return ciphertext;
+  }
+
+  decrypt(ciphertext: Uint8Array): Uint8Array {
+    if (ciphertext.length % 16) {
+        throw new TypeError("invalid ciphertext size (must be multiple of 16 bytes)");
+    }
+
+    const plaintext = new Uint8Array(ciphertext.length);
+    for (let i = 0; i < ciphertext.length; i += 16) {
+        const block = this.aes.decrypt(ciphertext.subarray(i, i + 16));
+
+        for (let j = 0; j < 16; j++) {
+          plaintext[i + j] = block[j] ^ this.#lastBlock[j];
+          this.#lastBlock[j] = ciphertext[i + j];
+        }
+    }
+
+    return plaintext;
+  }
+}