DES Encryption Tool

DES Encryption Calculator

Action

Operation Mode

Padding

Input Format

Output Format

Show First-Block Trace

Display 16 round states and subkeys

Key Format

IV Format

Expected Length Rule

Key and IV must decode to exactly 8 bytes.

Message / Cipher Input

Key

Initialization Vector

Example Data Table

Scenario	Action	Mode	Input Format	Message	Key	IV	Padding	Suggested Output
Basic text encryption	Encrypt	ECB	Text	OpenAI DES Demo	SecrKey!	InitVect	PKCS7	HEX
Legacy CBC block test	Encrypt	CBC	Hex	54657374426C6F636B313233	3132333435363738	4142434445464748	Zero	Base64
Ciphertext recovery	Decrypt	CBC	Base64	VGVzdERhdGE=	SecrKey!	InitVect	PKCS7	Text

Formula Used

DES operates on 64-bit blocks and uses a 56-bit effective key schedule. The tool applies the classical Feistel network shown below.

Initial permutation: IP(B)

Round split: L₀, R₀ = IP(B)

Round update: L_i = R_i-1

Round update: R_i = L_i-1 ⊕ f(R_i-1, K_i)

Feistel function: f(R, K) = P(S(E(R) ⊕ K))

ECB encryption: C_i = E_K(P_i)

CBC encryption: C_i = E_K(P_i ⊕ C_i-1)

CBC decryption: P_i = D_K(C_i) ⊕ C_i-1

Here, E expands 32 bits to 48, S compresses through eight S-boxes, P permutes the substituted bits, and each round uses one derived subkey.

How to Use This Calculator

Select whether you want to encrypt or decrypt data.
Choose ECB or CBC, then pick your padding rule.
Choose the input format for the message or ciphertext.
Enter an 8-byte key using text, hex, Base64, or binary.
If using CBC, enter an 8-byte initialization vector.
Select the output format you want to review or export.
Enable round tracing when you need first-block teaching details.
Press Submit to render the result above the form.
Use the CSV and PDF buttons to export the summary.

Frequently Asked Questions

1. What does this tool calculate?

It encrypts or decrypts data with the DES block cipher, supports ECB and CBC modes, applies chosen padding, and shows subkeys plus a first-block round trace.

2. Why must the key be eight bytes?

DES uses a 64-bit key container. Eight bytes equal 64 bits, although eight parity bits are reserved, leaving a 56-bit effective working key.

3. When should I use CBC instead of ECB?

Use CBC when you want repeated plaintext blocks to encrypt differently. ECB is easier for demonstrations, but CBC better illustrates chaining and block dependence.

4. What does the round trace show?

The trace lists the first block’s sixteen rounds, including updated left and right halves and the subkey used in each stage.

5. Which padding option is safest for mixed lengths?

PKCS7 is the most predictable option here because it stores the pad length explicitly. Zero padding may remove trailing zero bytes during decryption.

6. Can I enter binary or Base64 values?

Yes. The calculator accepts text, hex, Base64, and binary for message input, key input, and IV input, provided the decoded length rules are satisfied.

7. Is DES still recommended for modern security?

No. DES is considered obsolete because its effective 56-bit key is too small against modern brute-force attacks. Use it mainly for legacy learning.

8. What happens if I choose text output for ciphertext?

Ciphertext may contain unreadable bytes. The tool still returns the raw text output, but the HEX and Base64 views remain clearer for storage and comparison.