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cbc

Apache-2.0Release 1L3

AES-CBC (SP 800-38A §6.2) — confidentiality, padding is the caller's responsibility.

Module cbc | Source packages/front/fw/src/crypto/mode/cbc.js | Deps bitArray, aes | Worker-safe yes

CBC is unauthenticated: use gcm or chacha20poly1305 for AEAD. If CBC is required, layer an explicit MAC (encrypt-then-MAC).

Resolve

const cbc = runtime.resolve('cbc');
// Returns: { encrypt, decrypt }

API

Method Signature Returns
encrypt(prf, ptBa, ivBa) ({encrypt}, bitArray, bitArray) => bitArray | false Ciphertext (PT pre-padded by caller)
decrypt(prf, ctBa, ivBa) ({encrypt, decrypt}, bitArray, bitArray) => bitArray | false Plaintext (caller must unpad)

Examples

const { aes, cbc, pad, bitArray, random } = fw.runtime.resolveAll(['aes', 'cbc', 'pad', 'bitArray', 'random']);

const key = Array.from(bitArray.ui8_to_ba(random.bytes(32)));
const iv  = bitArray.ui8_to_ba(random.bytes(16));
const cipher = aes.fn(key);

const ptBa  = bitArray.ui8_to_ba(pad.pad(new TextEncoder().encode('Hello, CBC!')));
const ctBa  = cbc.encrypt(cipher, ptBa, iv);
const back  = cbc.decrypt(cipher, ctBa, iv);
const plain = pad.strip(bitArray.ba_to_ui8(back));

Worker Usage

const worker = fw.createWorker(
    function ({ libs, args }) {
        const cipher = libs.aes.fn(args[0]);
        self.postMessage(libs.cbc.encrypt(cipher, args[1], args[2]));
    },
    { dependencies: ['aes', 'cbc'], args: [keyWords, ptBa, ivBa] }
);

Notes

  • No AEAD: malleable (bit-flipping), no authentication. For AEAD, use GCM.
  • Caller padding: use utils/pad.js (PKCS#7 RFC 5652) or utils/aes_modes.cbc which handles padding.
  • MCT 6/6 byte-exact validated (FIPS 140-2 Annex C).

See also