DES Decrypt

Category: Symmetric Ciphers · Node Type ID: symmetric-des-decrypt

Single DES (56-bit effective, 8-byte key) Decryption

Overview

Decrypts ciphertext produced by DES Encrypt using the legacy 64-bit Single DES cipher (FIPS 46-3) with an 8-byte key across CBC, ECB, CTR, CFB, or OFB modes.

When to Use

Decrypting legacy 8-byte DES test vectors or smartcard tokens.

Parameter Configuration

Parameter (ID)	Type & Default	Visibility Condition	Description & Options
Cipher Mode `mode`	`select` Default: `ECB`	Always visible	Must match the Cipher Mode used during encryption. See Block Cipher Modes for full details. `ECB`: ECB (Electronic Codebook) `CBC`: CBC (Cipher Block Chaining)
Padding `padding`	`select` Default: `None`	Always visible	8-byte block unpadding scheme applied in `ECB` and `CBC` modes. See Padding Schemes for full details. `None`: None `ISO7816`: ISO/IEC 9797-1 Method 2 (ISO/IEC 7816-4) `ISO97971M3`: ISO/IEC 9797-1 Method 3 `PKCS7`: PKCS#5 (RFC 2898) `ANSIX923`: ANSI X9.23
Unify Errors `errorUnify`	`boolean` Default: `false` Supports Variable Reference (`$var`: `bool`)	Always visible	Replaces built-in errors with a custom error code/message when enabled.
Unified Error Code `errorUnifyCode`	`text` Default: `""` (empty) Supports Variable Reference (`$var`: `string`)	When `errorUnify` is `true`	Custom error code when Unify Errors is enabled.
Unified Error Message `errorUnifyMessage`	`text` Default: `""` (empty) Supports Variable Reference (`$var`: `string`)	When `errorUnify` is `true`	Custom error message when Unify Errors is enabled.

Port I/O Specification

See Ports & Connections for general wiring rules, data type colors, and dynamic port creation.

Input Ports

Port Nature: Fixed Input Ports (3 total; conditionally visible ports depend on parameter settings as shown below).

Port Name	Port ID	Data Type	Required	Visibility Condition	Description
`Key`	`key`	`Bytes` (8B)	Required	Always visible	8-byte DES key.
`Ciphertext`	`ciphertext`	`Bytes`	Required	Always visible	Encrypted byte array (`Uint8Array`) to decrypt.
`IV`	`iv`	`Bytes` (8B)	Optional	When `mode` is `CBC`	8-byte IV used during encryption (hidden in `ECB` mode; defaults to 8 zero bytes if unconnected).

Output Ports

Port Nature: Fixed Output Ports (1 total).

Port Name	Port ID	Data Type	Visibility Condition	Description
`Plaintext`	`plaintext`	`Bytes`	Always visible	Decrypted plaintext byte array (`Uint8Array`).

Error Cases

When any of the following conditions occurs at runtime, this node transitions to an ERROR state and downstream nodes connected to its outputs do not execute. Enabling Unify Errors (errorUnify) replaces all error codes below with your configured unified error code and message.

Error Code	Default Engine Message	Trigger Condition
`INVALID_KEY_LENGTH`	Invalid key length	Raised when `Key` is not 8 bytes.
`CIPHERTEXT_NOT_BLOCK_ALIGNED`	Ciphertext length is not a multiple of the block size	Raised in `ECB`/`CBC` mode when `Ciphertext` length is not a positive multiple of 8 bytes.
`INVALID_PADDING`	Invalid padding	Raised when the decrypted or input block's trailing bytes violate the structure of the selected padding standard.

Examples

Decrypting a Single DES Ciphertext

Recover plaintext using the same 8-byte key and mode.

Connect the 8-byte Key and Ciphertext to DES Decrypt with matching mode and padding.