Press n or j to go to the next uncovered block, b, p or k for the previous block.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 | 1x 1x 1x 12x 12x | import randomBytes from 'randombytes';
import type { IDecryptionModeOfOperation, IEncryptionModeOfOperation, IModeOfOperation } from './IModeOfOperation';
import { xor } from '../../utils/xor';
export class CTRMode implements IModeOfOperation {
public readonly encryption = new CTRMode.CTREncryptionMode();
public readonly decryption = new CTRMode.CTRDecryptionMode();
}
// istanbul ignore next
export namespace CTRMode {
export function incrementCounter(counter: Uint8Array): void {
for (let i = 15; i >= 0; i--) {
if (counter[i] !== 255) {
counter[i] += 1;
break;
} else {
counter[i] = 0;
if (i === 0)
counter[15] = 0;
}
}
}
export class CTREncryptionMode implements IEncryptionModeOfOperation {
private counter: Uint8Array | null = null;
public start(): Uint8Array {
this.counter = randomBytes(16);
return new Uint8Array(this.counter);
}
public combine(block: Uint8Array, encrypt: (block: Uint8Array) => Uint8Array): Uint8Array {
if (this.counter === null)
throw new Error('CTR encryption mode not started.');
incrementCounter(this.counter);
return xor(this.counter, encrypt(block));
}
public finish(): Uint8Array {
this.counter = null;
return new Uint8Array();
}
}
export class CTRDecryptionMode implements IDecryptionModeOfOperation {
private counter: Uint8Array | null = null;
public start(): Uint8Array {
this.counter = null;
return new Uint8Array();
}
public combine(block: Uint8Array, decrypt: (block: Uint8Array) => Uint8Array): Uint8Array {
if (this.counter === null) {
this.counter = new Uint8Array(block);
return new Uint8Array();
}
incrementCounter(this.counter);
const decrypted = decrypt(xor(this.counter, block));
return decrypted;
}
public finish(): Uint8Array {
this.counter = null;
return new Uint8Array();
}
}
}
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