3DES - Triple Data Encryption Standard

What is 3DES?

3DES stands for Triple Data Encryption Standard. It’s an enhancement of the original DES algorithm that applies the DES cipher three times to each data block. It was developed to overcome the security limitations of standard DES.

Why is 3DES useful?

  • 3DES was introduced as a temporary upgrade to DES until stronger standards (like AES) were developed.

  • It was useful because: * Provided improved security over single DES * Maintained backward compatibility * Was widely used in financial and government sectors * Played a key transitional role despite being slower and now outdated

How it works

  • Key generation – Uses two or three 56-bit keys (totaling 112 or 168 bits)

  • Encryption – Encrypts with Key1 → Decrypts with Key2 → Encrypts with Key3 (EDE sequence)

  • Transmission/Storage – Encrypted (ciphertext) blocks are transmitted or saved

  • Decryption – Reverses the process (Decrypt → Encrypt → Decrypt)

Where is 3DES used?

  • Still seen in: * Banking – Encrypting ATM PINs and transactions * Legacy systems – Where migration to AES hasn’t occurred * Secure file transfers – Older SFTP and SSH tools * VPNs and IPsec – Previously used in encrypted sessions * Smart cards and tokens – For secure storage and authentication

Which OSI layer does this protocol belong to?

  • 3DES operates at the Presentation Layer (Layer 6)

  • Manages encryption and decryption before data reaches the application

  • Ensures data confidentiality by transforming readable data into ciphertext

Topics in this section,

  • In this section, you are going to learn

  • Terminology

  • Version Info

3DES Version

3DES Number

Year

Core Idea / Contribution

Initial 3DES Proposal

RFC 1851

1995

Defined the use of Triple DES in IPsec ESP (EncryptDecryptEncrypt mode). First formal standardization of 3DES in network protocols.

ANSI Standardization

ANSI X9.52

1998

Defined modes of operation for Triple DES in financial and commercial systems. (Withdrawn in 2008)

NIST Recommendation

FIPS PUB 46-3

1999

Officially included Triple DES as a stronger alternative to DES.

NIST TDEA Guidelines

NIST SP 800-67 Rev. 2

2017

Provided updated recommendations for using Triple DES securely. Withdrawn in 2024 due to security concerns.

Deprecation Notice

RFC 8429

2018

Deprecated Triple DES and RC4 in Kerberos due to weakening cryptographic strength 1.

Security Advisory

CVE-2016-2183

2016

Identified vulnerabilities in DES and 3DES (Sweet32 attack), leading to deprecation by NIST.

  • Setup

  • Setup

3DES Encryption Packet

S.No

Protocol Packets

Description

Size(Bytes)

1

3DES Encryption Packet

Used to encrypt a 64-bit block of plaintext using three DES operations.

336

Plaintext Block

The original data to be encrypted.

8

Key 1

First 56-bit DES key (plus 8 parity bits).

8

Key 2

Second 56-bit DES key (plus 8 parity bits).

8

Key 3 (optional)

Third 56-bit DES key (optional in 2-key 3DES).

8 (or reused)

Initial Permutation (IP)

Bit-level permutation applied before encryption.

8 (reordered)

Round Keys (3 sets)

16 subkeys per key 3 keys = 48 subkeys total.

288

Encryption Steps

Encrypt with Key 1 Decrypt with Key 2 Encrypt with Key 3 (EDE mode).

Internal

Final Permutation (FP)

Bit-level permutation applied after encryption.

8 (reordered)

Ciphertext Block

The final encrypted output.

8

3DES Decryption Packet

S.No

Protocol Packets

Description

Size(Bytes)

2

3DES Decryption Packet

Used to decrypt a 64-bit ciphertext block using the same three keys in reverse order.

336

Ciphertext Block

The encrypted data to be decrypted.

8

Key 1

First 56-bit DES key (used last in decryption).

8

Key 2

Second 56-bit DES key (used in the middle).

8

Key 3 (optional)

Third 56-bit DES key (used first in decryption).

8 (or reused)

Initial Permutation (IP)

Bit-level permutation applied before decryption.

8 (reordered)

Round Keys (3 sets)

48 subkeys used in reverse order.

288

Decryption Steps

Decrypt with Key 3 Encrypt with Key 2 Decrypt with Key 1.

Internal

Final Permutation (FP)

Bit-level permutation applied after decryption.

8 (reordered)

Plaintext Block

The original data recovered after decryption.

8

S.no

Use Case

Description

1

Banking & Financial Systems

Used to encrypt ATM PINs, card transactions, and interbank communications.

2

EMV Smart Cards

Widely used in chip-based payment cards for secure authentication and encryption.

3

Legacy VPNs and IPsec

Used in older VPNs and IPsec implementations for encrypting network traffic.

4

Secure File Transfer

Employed in older SFTP and SSH systems for encrypting files in transit.

5

Government Systems

Adopted in secure government communications before AES became the standard.

6

Token-Based Authentication

Used in hardware tokens and secure ID systems for encrypting credentials.

7

Mainframe Systems

Still used in legacy IBM mainframes and enterprise systems for data protection.

8

Digital Signatures

Used in some older digital signature schemes for secure hashing and encryption.

9

Secure Messaging

Applied in early secure messaging platforms for encrypting message content.

10

Data-at-Rest Encryption

Used in older disk and database encryption tools to protect stored data.

S.no

Feature

Description

1

Symmetric Key Cipher

Uses the same key (or key set) for both encryption and decryption.

2

Block Cipher

Operates on 64-bit (8-byte) blocks of data.

3

Keying Options

Supports 2-key (112-bit) and 3-key (168-bit) configurations.

4

Triple Encryption

Applies DES three times: Encrypt Decrypt Encrypt (EDE mode).

5

Backward Compatibility

Compatible with single DES when all three keys are the same.

6

Feistel Structure

Inherits the 16-round Feistel network from DES for each encryption step.

7

Stronger than DES

More secure than DES due to longer effective key length.

8

Slower than AES

Computationally slower due to triple processing, especially in software.

9

Still Used in Legacy Systems

Common in older banking, government, and embedded systems.

10

Being Phased Out

Considered deprecated by NIST and replaced by AES in modern systems.

Symmetric Key Cipher - Testcases

#

Test Case

Description

Expected Result

1

Valid Encryption-Decryption

Encrypt and decrypt with same key

Original plaintext recovered

2

Invalid Key for Decryption

Use wrong key for decryption

Decryption fails or returns garbage

3

Empty Plaintext

Encrypt empty string

Encrypted output is valid

4

Empty Key

Use empty key

Error or exception raised

5

Maximum Key Length

Use max supported key

Encryption succeeds

6

Minimum Key Length

Use min supported key

Encryption succeeds

7

Non-ASCII Characters

Encrypt Unicode text

Decryption returns correct Unicode

8

Binary Data Encryption

Encrypt binary file

Decryption restores original file

9

Repeated Encryption

Encrypt same plaintext twice

Same ciphertext (ECB) or different (CBC)

10

Key Reuse

Reuse key across sessions

Consistent results

11

Key Rotation

Change key mid-session

Decryption fails with old key

12

Key Expiry

Use expired key

Operation denied

13

Key Storage

Store key securely

Key not exposed in logs

14

Key Retrieval

Retrieve key from secure store

Key retrieved successfully

15

Key Tampering

Modify stored key

Decryption fails

16

Key Format Validation

Use invalid key format

Error raised

17

Large Plaintext

Encrypt large file (e.g., 1GB)

Decryption successful

18

Small Plaintext

Encrypt 1-byte message

Decryption successful

19

Null Input

Pass null as input

Error or handled gracefully

20

Key Collision

Use two keys with same hash

Different encryption results

21

Initialization Vector (IV) Use

Use IV in CBC mode

Decryption requires same IV

22

IV Mismatch

Use wrong IV

Decryption fails

23

IV Reuse

Reuse IV with same key

Security warning

24

Mode of Operation: ECB

Encrypt using ECB

Identical blocks produce same ciphertext

25

Mode of Operation: CBC

Encrypt using CBC

Ciphertext differs for same plaintext

26

Mode of Operation: CFB

Encrypt using CFB

Stream encryption successful

27

Mode of Operation: OFB

Encrypt using OFB

Output matches expected

28

Mode of Operation: CTR

Encrypt using CTR

Output matches expected

29

Padding Enabled

Encrypt with padding

Decryption removes padding

30

Padding Disabled

Encrypt without padding

Error if input not block-aligned

31

Incorrect Padding

Decrypt with wrong padding

Decryption fails

32

Key Length Mismatch

Use unsupported key length

Error raised

33

Ciphertext Integrity

Modify ciphertext

Decryption fails or returns garbage

34

Ciphertext Replay

Replay encrypted message

Decryption still works

35

Performance Benchmark

Measure encryption time

Within acceptable limits

36

Multi-threaded Encryption

Encrypt in parallel threads

No data corruption

37

Concurrent Sessions

Multiple encryptions with same key

All succeed independently

38

Cross-Platform Compatibility

Encrypt on one OS, decrypt on another

Decryption successful

39

Language Interoperability

Encrypt in Python, decrypt in Java

Decryption successful

40

Key Sharing

Share key securely

Key not exposed in transit

41

Key Agreement Protocol

Use Diffie-Hellman for key exchange

Shared key established

42

Key Derivation Function

Derive key from password

Key generated correctly

43

Key Strength Validation

Check entropy of key

Meets security threshold

44

Brute Force Resistance

Attempt brute force

Infeasible within time limit

45

Known Plaintext Attack

Encrypt known input

Ciphertext does not reveal key

46

Chosen Plaintext Attack

Encrypt attacker-chosen input

No key leakage

47

Ciphertext-Only Attack

Analyze ciphertext only

Key remains secure

48

Side-Channel Attack Simulation

Measure timing/power

No key leakage

49

Logging Behavior

Ensure no key/ciphertext in logs

Logs are clean

50

Compliance Check

Validate against FIPS/NIST

Cipher meets standards

Block Cipher - Testcases

#

Test Case

Description

Expected Result

1

Exact Block Size Input

Encrypt 8-byte input

Encrypted successfully

2

Less Than Block Size

Encrypt 5-byte input

Padding applied

3

More Than Block Size

Encrypt 10-byte input

Split into blocks

4

Multiple Blocks

Encrypt 24-byte input

3 blocks encrypted

5

Empty Input

Encrypt empty string

No output or error

6

Block Size Alignment

Input aligned to 64-bit

No padding needed

7

Non-Aligned Input

Input not aligned

Padding added

8

Padding Scheme: PKCS5

Use PKCS5 padding

Padding applied correctly

9

Padding Scheme: Zero Padding

Use zero padding

Padding applied correctly

10

Padding Scheme: None

Disable padding

Error if input not aligned

11

Decrypt with Padding

Decrypt padded ciphertext

Original plaintext recovered

12

Decrypt Without Padding

Decrypt unpadded ciphertext

Works only if input aligned

13

Encrypt Binary Data

Encrypt 64-bit binary

Encrypted correctly

14

Encrypt Text Data

Encrypt 8-character string

Encrypted correctly

15

Encrypt Unicode Data

Encrypt 8-byte Unicode

Encrypted correctly

16

Encrypt with ECB Mode

Use ECB mode

Identical blocks produce same ciphertext

17

Encrypt with CBC Mode

Use CBC mode

Ciphertext differs

18

Encrypt with CFB Mode

Use CFB mode

Stream-like encryption

19

Encrypt with OFB Mode

Use OFB mode

Output matches expected

20

Encrypt with CTR Mode

Use CTR mode

Output matches expected

21

Encrypt 64-bit Integer

Encrypt integer value

Encrypted correctly

22

Encrypt 64-bit Float

Encrypt float value

Encrypted correctly

23

Encrypt 64-bit Hex

Encrypt hex string

Encrypted correctly

24

Encrypt 64-bit Binary File

Encrypt 8-byte file

File encrypted

25

Encrypt 128-bit Input

Encrypt 16-byte input

2 blocks encrypted

26

Encrypt 192-bit Input

Encrypt 24-byte input

3 blocks encrypted

27

Encrypt 256-bit Input

Encrypt 32-byte input

4 blocks encrypted

28

Encrypt 512-bit Input

Encrypt 64-byte input

8 blocks encrypted

29

Encrypt 1MB File

Encrypt large file

All blocks processed

30

Encrypt with IV

Use IV in CBC mode

IV used correctly

31

Encrypt with Wrong IV

Use incorrect IV

Decryption fails

32

Encrypt with Same IV

Reuse IV

Security warning

33

Encrypt with Random IV

Generate new IV

IV stored or transmitted

34

Encrypt with Static Key

Use same key repeatedly

Consistent encryption

35

Encrypt with Rotating Key

Change key per block

Different ciphertexts

36

Encrypt with Weak Key

Use known weak key

Warning or error

37

Encrypt with Strong Key

Use high-entropy key

Encryption secure

38

Encrypt with Corrupted Block

Corrupt one block

Only that block affected

39

Encrypt with Block Loss

Drop one block

Decryption incomplete

40

Encrypt with Block Reordering

Shuffle blocks

Decryption fails

41

Encrypt with Block Duplication

Duplicate a block

Decryption shows repeated data

42

Encrypt with Block Injection

Inject fake block

Decryption shows extra data

43

Encrypt with Block Truncation

Truncate ciphertext

Decryption fails

44

Encrypt with Block Expansion

Add extra block

Decryption shows garbage

45

Encrypt with Block Compression

Compress before encryption

Decryption restores original

46

Encrypt with Block Integrity Check

Add checksum

Tampering detected

47

Encrypt with Block Authentication

Use MAC

Message authenticated

48

Encrypt with Block Logging

Log each block

Logs show block boundaries

49

Encrypt with Block Timing

Measure time per block

Performance benchmarked

50

Encrypt with Block Size Mismatch

Use wrong block size

Error raised

Keying Options - Testcases

#

Test Case

Description

Expected Result

1

Valid 3-Key Encryption

Use 3 unique keys

Encryption successful

2

Valid 2-Key Encryption

Use 2 keys (K1 = K3)

Encryption successful

3

Invalid Key Length

Use 100-bit key

Error raised

4

Single Key (DES Mode)

Use same key for K1, K2, K3

Equivalent to DES

5

Null Key

Use null key

Error or warning

6

All Keys Identical

K1 = K2 = K3

Reduced security

7

K1 K2 = K3

Use 2-key variant

Encryption valid

8

K1 = K2 K3

Invalid 2-key config

Warning or fallback

9

K1 K2 K3

Use 3-key variant

Full 168-bit encryption

10

Key Format: Hex

Provide keys in hex

Accepted

11

Key Format: Binary

Provide keys in binary

Accepted

12

Key Format: ASCII

Provide keys in ASCII

Converted and accepted

13

Key Format: Invalid

Use unsupported format

Error raised

14

Key Length: 112-bit

Use 2-key config

Encryption successful

15

Key Length: 168-bit

Use 3-key config

Encryption successful

16

Key Length: 56-bit

Use single DES key

Warning or fallback

17

Key Rotation

Change keys periodically

Encryption remains valid

18

Key Reuse

Reuse same keys

Consistent output

19

Key Expiry

Use expired key

Operation denied

20

Key Tampering

Modify key during use

Decryption fails

21

Key Storage

Store keys securely

Keys not exposed

22

Key Retrieval

Retrieve keys from vault

Keys loaded correctly

23

Key Corruption

Corrupt one key

Decryption fails

24

Key Comparison

Compare 2-key vs 3-key output

Different ciphertexts

25

Key Entropy Check

Check randomness

High entropy required

26

Key Collision

Use keys with same hash

Different encryption results

27

Key Derivation

Derive keys from passphrase

Keys generated correctly

28

Key Injection

Inject keys into hardware

Keys accepted

29

Key Export

Export keys securely

Keys encrypted

30

Key Import

Import keys

Keys validated

31

Key Backup

Backup keys

Backup successful

32

Key Restore

Restore from backup

Keys restored

33

Key Logging

Ensure keys not logged

Logs clean

34

Key Audit Trail

Track key usage

Audit complete

35

Key Access Control

Restrict key access

Unauthorized blocked

36

Key Sharing

Share keys securely

Keys encrypted in transit

37

Key Agreement Protocol

Use Diffie-Hellman

Shared key established

38

Key Validation

Validate key structure

Keys accepted

39

Key Mismatch

Use wrong key for decryption

Decryption fails

40

Key Compatibility

Use same keys across platforms

Compatible

41

Key Performance Test

Encrypt with 2-key vs 3-key

2-key is faster

42

Key Usage Logging

Log key usage events

Logs complete

43

Key Policy Enforcement

Enforce key rotation policy

Policy applied

44

Key Strength Enforcement

Reject weak keys

Error raised

45

Key Format Conversion

Convert ASCII to binary

Conversion successful

46

Key Initialization Vector

Use IV with keys

IV used correctly

47

Key with CBC Mode

Use 2-key in CBC mode

Encryption successful

48

Key with ECB Mode

Use 3-key in ECB mode

Encryption successful

49

Key with OFB Mode

Use 2-key in OFB mode

Encryption successful

50

Key with CTR Mode

Use 3-key in CTR mode

Encryption successful

Triple Encryption - Testcases

#

Test Case

Description

Expected Result

1

Valid EDE Encryption

Encrypt using 3 unique keys

Ciphertext generated

2

Valid EDE Decryption

Decrypt using same 3 keys

Original plaintext recovered

3

EDE with 2-Key Mode

Use K1 = K3

Encryption and decryption successful

4

EDE with 3-Key Mode

Use K1 K2 K3

Full 3DES encryption

5

EDE with Identical Keys

K1 = K2 = K3

Equivalent to single DES

6

EDE with Invalid Key Length

Use 100-bit key

Error raised

7

EDE with Null Key

Use null key

Operation fails

8

EDE with Empty Input

Encrypt empty string

No output or error

9

EDE with 64-bit Input

Encrypt 8-byte block

Encrypted successfully

10

EDE with 128-bit Input

Encrypt 16-byte block

Two blocks encrypted

11

EDE with Binary Data

Encrypt binary file

File encrypted

12

EDE with Text Data

Encrypt string

Ciphertext returned

13

EDE with Unicode Data

Encrypt Unicode string

Decryption returns original

14

EDE with ECB Mode

Use ECB mode

Identical blocks produce same ciphertext

15

EDE with CBC Mode

Use CBC mode

Ciphertext varies with IV

16

EDE with CFB Mode

Use CFB mode

Stream-like encryption

17

EDE with OFB Mode

Use OFB mode

Output matches expected

18

EDE with CTR Mode

Use CTR mode

Output matches expected

19

EDE with IV

Use initialization vector

IV required for decryption

20

EDE with Wrong IV

Use incorrect IV

Decryption fails

21

EDE with No Padding

Input not block-aligned

Error raised

22

EDE with PKCS5 Padding

Use padding scheme

Padding added and removed correctly

23

EDE with Zero Padding

Use zero padding

Padding handled correctly

24

EDE with Corrupted Ciphertext

Modify ciphertext

Decryption fails

25

EDE with Corrupted Key

Modify key

Decryption fails

26

EDE with Key Rotation

Change keys mid-session

Decryption fails with old key

27

EDE with Key Reuse

Reuse same keys

Consistent output

28

EDE with Key Expiry

Use expired key

Operation denied

29

EDE with Key Tampering

Tamper with key

Decryption fails

30

EDE with Key Format: Hex

Provide keys in hex

Encryption successful

31

EDE with Key Format: Binary

Provide keys in binary

Encryption successful

32

EDE with Key Format: ASCII

Provide keys in ASCII

Converted and accepted

33

EDE with Weak Key

Use known weak key

Warning or error

34

EDE with Strong Key

Use high-entropy key

Encryption secure

35

EDE with Logging Enabled

Log encryption steps

Logs show EDE sequence

36

EDE with Performance Benchmark

Measure time taken

Within acceptable limits

37

EDE with Multi-threading

Encrypt in parallel

No data corruption

38

EDE with Cross-Platform Use

Encrypt on one OS, decrypt on another

Decryption successful

39

EDE with Language Interop

Encrypt in Python, decrypt in Java

Decryption successful

40

EDE with Key Derivation

Derive keys from password

Keys generated correctly

41

EDE with Key Agreement

Use DH to share keys

Shared key used in EDE

42

EDE with Key Storage

Store keys securely

Keys not exposed

43

EDE with Key Retrieval

Retrieve keys from vault

Keys loaded correctly

44

EDE with Key Audit

Track key usage

Audit complete

45

EDE with Compliance Check

Validate against FIPS

EDE mode compliant

46

EDE with Ciphertext Replay

Replay encrypted message

Decryption still works

47

EDE with Side-Channel Attack

Simulate timing attack

No key leakage

48

EDE with Brute Force Attempt

Try all key combinations

Infeasible within time limit

49

EDE with Known Plaintext

Encrypt known input

Ciphertext does not reveal key

50

EDE with Chosen Plaintext

Encrypt attacker-chosen input

No key leakage

Backward Compatibility - Testcases

#

Test Case

Description

Expected Result

1

All Keys Identical

Set K1 = K2 = K3

Output matches DES

2

Encrypt with DES

Encrypt using DES

Output matches 3DES with identical keys

3

Decrypt with DES

Decrypt using DES

Output matches 3DES decryption

4

Encrypt with 3DES (K1=K2=K3)

Use same key for all

Equivalent to DES

5

Encrypt with 3DES (K1K2K3)

Use different keys

Output differs from DES

6

Encrypt with 3DES (K1=K3K2)

Use 2-key mode

Output differs from DES

7

Encrypt with 3DES (K1K2=K3)

Invalid DES compatibility

Output differs

8

Encrypt with 3DES (K1K2K3)

Use 3-key mode

Not backward compatible

9

Decrypt with DES (3DES ciphertext)

Use DES to decrypt 3DES output

Decryption fails

10

Encrypt with DES, Decrypt with 3DES

Use same key for all

Decryption successful

11

Encrypt with 3DES, Decrypt with DES

Use same key for all

Decryption successful

12

Encrypt 64-bit Block

Use DES and 3DES (same keys)

Outputs match

13

Encrypt 128-bit Block

Compare DES and 3DES

Outputs match per block

14

Encrypt with ECB Mode

Use DES and 3DES

Outputs match

15

Encrypt with CBC Mode

Use same IV and keys

Outputs match

16

Encrypt with CFB Mode

Use same IV and keys

Outputs match

17

Encrypt with OFB Mode

Use same IV and keys

Outputs match

18

Encrypt with CTR Mode

Use same nonce and keys

Outputs match

19

Encrypt Binary File

Use DES and 3DES

Files match

20

Encrypt Text File

Use DES and 3DES

Files match

21

Encrypt Unicode Text

Use DES and 3DES

Outputs match

22

Encrypt with Hex Key

Use same hex key

Outputs match

23

Encrypt with Binary Key

Use same binary key

Outputs match

24

Encrypt with ASCII Key

Use same ASCII key

Outputs match

25

Encrypt with Weak Key

Use known weak DES key

Warning issued

26

Encrypt with Strong Key

Use high-entropy key

Outputs match

27

Encrypt with Null Key

Use all-zero key

Outputs match

28

Encrypt with All 1s Key

Use all-one key

Outputs match

29

Encrypt with Random Key

Use same random key

Outputs match

30

Encrypt with Reused Key

Reuse same key

Outputs match

31

Encrypt with Expired Key

Use expired key

Operation denied

32

Encrypt with Corrupted Key

Modify key

Outputs differ

33

Encrypt with Key Rotation

Rotate key mid-session

Outputs differ

34

Encrypt with Key Tampering

Tamper with key

Outputs differ

35

Encrypt with Key Derivation

Derive same key

Outputs match

36

Encrypt with Key Agreement

Share same key

Outputs match

37

Encrypt with Key Import

Import same key

Outputs match

38

Encrypt with Key Export

Export and reuse key

Outputs match

39

Encrypt with Key Backup

Restore same key

Outputs match

40

Encrypt with Key Logging

Ensure key not logged

Logs clean

41

Encrypt with Key Audit

Track key usage

Audit confirms match

42

Encrypt with Key Policy

Enforce same key policy

Outputs match

43

Encrypt with Compliance Mode

Use FIPS-compliant DES

Outputs match

44

Encrypt with Hardware Module

Use HSM for DES and 3DES

Outputs match

45

Encrypt with Software Library

Use OpenSSL for both

Outputs match

46

Encrypt with Java and Python

Use same key

Outputs match

47

Encrypt with Cross-Platform Tools

Use same key

Outputs match

48

Encrypt with Legacy System

Use DES-compatible 3DES

Outputs match

49

Encrypt with Modern System

Use 3DES in DES mode

Outputs match

50

Encrypt with Mixed Systems

DES on one, 3DES on another

Interoperability confirmed

** Feistel Structure - Testcases**

#

Test Case

Description

Expected Result

1

16 Rounds Executed

Run one DES step

All 16 rounds completed

2

Round Function Consistency

Use same input twice

Same output per round

3

Round Key Variation

Use different keys per round

Different outputs

4

Round Key Reuse

Reuse round keys

Consistent output

5

Round Key Schedule

Generate 16 keys

Keys derived correctly

6

Initial Permutation

Apply IP before rounds

IP applied correctly

7

Final Permutation

Apply FP after rounds

FP applied correctly

8

Expansion Function

Expand 32-bit half block

Expanded to 48 bits

9

S-Box Substitution

Apply S-boxes

Output is 32 bits

10

P-Box Permutation

Apply P-box

Bits permuted correctly

11

XOR with Round Key

XOR expanded block with key

XOR result correct

12

Left and Right Swap

Swap halves after each round

Swap successful

13

Round Output Logging

Log each round output

All rounds logged

14

Round Key Logging

Log round keys

All keys logged

15

Round Timing

Measure time per round

Time within expected range

16

Round Fault Injection

Inject fault in round

Output deviates

17

Round Bypass

Skip a round

Output incorrect

18

Round Repetition

Repeat a round

Output deviates

19

Round Order Change

Change round order

Output incorrect

20

Round Function Tampering

Modify F-function

Output deviates

21

Round Function Isolation

Test F-function alone

Output as expected

22

Round Key Corruption

Corrupt one round key

Output deviates

23

Round Key Reversal

Reverse key order

Decryption fails

24

Round Key Inversion

Invert key bits

Output deviates

25

Round Key All Zeros

Use zero key

Output predictable

26

Round Key All Ones

Use all-one key

Output predictable

27

Round Key Random

Use random keys

Output unpredictable

28

Round Key Weak

Use weak DES keys

Warning issued

29

Round Key Strong

Use high-entropy keys

Output secure

30

Round Key Schedule Validation

Validate key schedule

Keys derived correctly

31

Round Function Reversibility

Reverse round steps

Original input recovered

32

Round Function Symmetry

Test symmetry

Output not symmetric

33

Round Function Avalanche

Flip 1 input bit

>50% output bits change

34

Round Function Bit Sensitivity

Flip 1 key bit

Output changes significantly

35

Round Function Input Size

Use 64-bit input

Accepted

36

Round Function Output Size

Output is 64 bits

Validated

37

Round Function with Padding

Input with padding

Padding handled

38

Round Function with No Padding

Input aligned

No padding needed

39

Round Function with ECB Mode

Use ECB

Rounds executed

40

Round Function with CBC Mode

Use CBC

Rounds executed

41

Round Function with CFB Mode

Use CFB

Rounds executed

42

Round Function with OFB Mode

Use OFB

Rounds executed

43

Round Function with CTR Mode

Use CTR

Rounds executed

44

Round Function with IV

Use IV

IV applied before rounds

45

Round Function with Fault Tolerance

Simulate fault

Error detected

46

Round Function with Logging Disabled

Disable logs

No round logs

47

Round Function with Debug Mode

Enable debug

Round internals visible

48

Round Function with Hardware Acceleration

Use hardware

Faster execution

49

Round Function with Software Library

Use OpenSSL

Rounds executed correctly

50

Round Function with Compliance Check

Validate against DES spec

All steps compliant

Stronger than DES - Testcases

Stronger than DES

#

Test Case

Description

Expected Result

1

Encrypt with DES

Use 56-bit DES key

Ciphertext generated

2

Encrypt with 3DES

Use 168-bit key

Stronger ciphertext

3

Brute Force DES

Attempt brute force on DES

Key cracked quickly

4

Brute Force 3DES

Attempt brute force on 3DES

Infeasible within time limit

5

Key Length Comparison

Compare DES and 3DES keys

3DES key is longer

6

Key Space Comparison

Calculate key space

3DES has larger key space

7

Known Plaintext Attack on DES

Encrypt known input

DES vulnerable

8

Known Plaintext Attack on 3DES

Encrypt known input

3DES resists attack

9

Chosen Plaintext Attack on DES

Encrypt attacker-chosen input

DES vulnerable

10

Chosen Plaintext Attack on 3DES

Encrypt attacker-chosen input

3DES resists attack

11

Ciphertext-Only Attack on DES

Analyze ciphertext

DES key guessed

12

Ciphertext-Only Attack on 3DES

Analyze ciphertext

Key remains secure

13

Differential Cryptanalysis on DES

Apply differential analysis

DES cracked

14

Differential Cryptanalysis on 3DES

Apply same method

3DES resists

15

Linear Cryptanalysis on DES

Apply linear analysis

DES cracked

16

Linear Cryptanalysis on 3DES

Apply same method

3DES resists

17

DES Key Reuse

Reuse DES key

Predictable output

18

3DES Key Reuse

Reuse 3DES key

Still secure

19

DES Key Collision

Use weak DES keys

Collision possible

20

3DES Key Collision

Use weak 3DES keys

Collision unlikely

21

DES with ECB Mode

Encrypt repeated blocks

Identical ciphertext

22

3DES with ECB Mode

Encrypt repeated blocks

Still vulnerable, but stronger

23

DES with CBC Mode

Encrypt with IV

Ciphertext varies

24

3DES with CBC Mode

Encrypt with IV

Ciphertext more secure

25

DES with Random Key

Use random 56-bit key

Encryption weak

26

3DES with Random Key

Use random 168-bit key

Encryption strong

27

DES with All-Zero Key

Use zero key

Predictable output

28

3DES with All-Zero Keys

Use zero keys

Still stronger than DES

29

DES with All-One Key

Use all-one key

Predictable output

30

3DES with All-One Keys

Use all-one keys

Still stronger

31

DES with Weak Key

Use known weak key

Easily broken

32

3DES with Weak Key

Use weak key set

Still more secure

33

DES with Hardware Acceleration

Encrypt with DES chip

Fast but insecure

34

3DES with Hardware Acceleration

Encrypt with 3DES chip

Secure and fast

35

DES with Software Library

Use OpenSSL DES

Works but outdated

36

3DES with Software Library

Use OpenSSL 3DES

Secure

37

DES in Legacy System

Encrypt legacy data

Compatible but weak

38

3DES in Modern System

Encrypt sensitive data

Secure

39

DES in VPN

Use DES for tunnel

Not recommended

40

3DES in VPN

Use 3DES for tunnel

Acceptable security

41

DES in TLS

Use DES cipher suite

Deprecated

42

3DES in TLS

Use 3DES cipher suite

Still supported (with caution)

43

DES in SSH

Use DES for session

Not allowed

44

3DES in SSH

Use 3DES for session

Allowed

45

DES in File Encryption

Encrypt file

Weak protection

46

3DES in File Encryption

Encrypt file

Stronger protection

47

DES in Email Encryption

Encrypt message

Vulnerable

48

3DES in Email Encryption

Encrypt message

Secure

49

DES in Database Encryption

Encrypt records

Not secure

50

3DES in Database Encryption

Encrypt records

Acceptable security

Slower than AES - Testcases

#

Test Case

Description

Expected Result

1

Encrypt 1KB with 3DES

Measure time

Slower than AES

2

Encrypt 1KB with AES

Measure time

Faster than 3DES

3

Encrypt 10MB File with 3DES

Benchmark

Noticeable delay

4

Encrypt 10MB File with AES

Benchmark

Faster completion

5

Decrypt 1KB with 3DES

Measure time

Slower than AES

6

Decrypt 1KB with AES

Measure time

Faster than 3DES

7

CPU Usage 3DES

Monitor CPU during encryption

Higher usage

8

CPU Usage AES

Monitor CPU during encryption

Lower usage

9

Memory Usage 3DES

Monitor memory

Slightly higher

10

Memory Usage AES

Monitor memory

Efficient usage

11

Encrypt in Software (3DES)

Use software library

Slower

12

Encrypt in Software (AES)

Use software library

Faster

13

Encrypt in Hardware (3DES)

Use hardware module

Improved speed

14

Encrypt in Hardware (AES)

Use hardware module

Very fast

15

Encrypt with ECB Mode (3DES)

Measure time

Slower

16

Encrypt with ECB Mode (AES)

Measure time

Faster

17

Encrypt with CBC Mode (3DES)

Measure time

Slower

18

Encrypt with CBC Mode (AES)

Measure time

Faster

19

Encrypt with CFB Mode (3DES)

Measure time

Slower

20

Encrypt with CFB Mode (AES)

Measure time

Faster

21

Encrypt with OFB Mode (3DES)

Measure time

Slower

22

Encrypt with OFB Mode (AES)

Measure time

Faster

23

Encrypt with CTR Mode (3DES)

Measure time

Slower

24

Encrypt with CTR Mode (AES)

Measure time

Faster

25

Encrypt 1000 Messages (3DES)

Batch encrypt

Slower throughput

26

Encrypt 1000 Messages (AES)

Batch encrypt

Higher throughput

27

Encrypt with 2-Key 3DES

Use 112-bit key

Still slower than AES

28

Encrypt with 3-Key 3DES

Use 168-bit key

Even slower

29

Encrypt with AES-128

Use 128-bit key

Fastest

30

Encrypt with AES-256

Use 256-bit key

Still faster than 3DES

31

Encrypt on Mobile (3DES)

Use mobile CPU

Noticeable lag

32

Encrypt on Mobile (AES)

Use mobile CPU

Smooth performance

33

Encrypt on Embedded Device (3DES)

Use IoT device

High latency

34

Encrypt on Embedded Device (AES)

Use IoT device

Acceptable latency

35

Encrypt with OpenSSL (3DES)

Use OpenSSL CLI

Slower

36

Encrypt with OpenSSL (AES)

Use OpenSSL CLI

Faster

37

Encrypt with Python (3DES)

Use PyCryptodome

Slower

38

Encrypt with Python (AES)

Use PyCryptodome

Faster

39

Encrypt with Java (3DES)

Use JCE

Slower

40

Encrypt with Java (AES)

Use JCE

Faster

41

Encrypt with Node.js (3DES)

Use crypto module

Slower

42

Encrypt with Node.js (AES)

Use crypto module

Faster

43

Encrypt with Go (3DES)

Use Go crypto

Slower

44

Encrypt with Go (AES)

Use Go crypto

Faster

45

Encrypt with Rust (3DES)

Use RustCrypto

Slower

46

Encrypt with Rust (AES)

Use RustCrypto

Faster

47

Encrypt with C++ (3DES)

Use Crypto++

Slower

48

Encrypt with C++ (AES)

Use Crypto++

Faster

49

Encrypt with .NET (3DES)

Use System.Security

Slower

50

Encrypt with .NET (AES)

Use System.Security

Faster

Systems - Testcases

Used in Legacy Systems

#

Test Case

Description

Expected Result

1

Encrypt with Legacy Banking App

Use 3DES in old banking software

Encryption successful

2

Decrypt with Legacy Banking App

Decrypt 3DES ciphertext

Plaintext recovered

3

Encrypt with Legacy ATM

Use 3DES in ATM firmware

Transaction encrypted

4

Decrypt with Legacy ATM

Decrypt PIN block

PIN verified

5

Encrypt with Legacy POS

Use 3DES in point-of-sale terminal

Data secured

6

Decrypt with Legacy POS

Decrypt transaction data

Data readable

7

Encrypt with Legacy Smart Card

Use 3DES on card chip

Data encrypted

8

Decrypt with Legacy Smart Card

Read encrypted data

Data decrypted

9

Encrypt with Legacy HSM

Use 3DES in hardware security module

Operation successful

10

Decrypt with Legacy HSM

Decrypt using 3DES key

Data recovered

11

Encrypt with Legacy Government App

Use 3DES in secure messaging

Message encrypted

12

Decrypt with Legacy Government App

Decrypt message

Message readable

13

Encrypt with Legacy VPN

Use 3DES in IPsec tunnel

Tunnel established

14

Decrypt with Legacy VPN

Receive 3DES-encrypted packets

Packets decrypted

15

Encrypt with Legacy Database

Use 3DES for column encryption

Data secured

16

Decrypt with Legacy Database

Read encrypted column

Data decrypted

17

Encrypt with Legacy Email Gateway

Use 3DES for S/MIME

Email encrypted

18

Decrypt with Legacy Email Gateway

Decrypt S/MIME message

Email readable

19

Encrypt with Legacy File System

Use 3DES for file encryption

File secured

20

Decrypt with Legacy File System

Read encrypted file

File decrypted

21

Encrypt with Legacy Firmware

Use 3DES in embedded device

Data encrypted

22

Decrypt with Legacy Firmware

Decrypt stored data

Data readable

23

Encrypt with Legacy Token

Use 3DES in OTP token

OTP generated

24

Decrypt with Legacy Token Server

Validate OTP

OTP accepted

25

Encrypt with Legacy Payment Gateway

Use 3DES for transaction

Payment processed

26

Decrypt with Legacy Payment Gateway

Read transaction data

Data decrypted

27

Encrypt with Legacy Middleware

Use 3DES in message bus

Message encrypted

28

Decrypt with Legacy Middleware

Read encrypted message

Message decrypted

29

Encrypt with Legacy Java App

Use JCE with 3DES

Encryption successful

30

Decrypt with Legacy Java App

Decrypt using JCE

Decryption successful

31

Encrypt with Legacy .NET App

Use 3DES in .NET Framework

Encryption successful

32

Decrypt with Legacy .NET App

Decrypt using .NET

Decryption successful

33

Encrypt with Legacy C++ App

Use Crypto++ 3DES

Data encrypted

34

Decrypt with Legacy C++ App

Decrypt with Crypto++

Data decrypted

35

Encrypt with Legacy Python Script

Use PyCrypto 3DES

Data encrypted

36

Decrypt with Legacy Python Script

Decrypt with PyCrypto

Data decrypted

37

Encrypt with Legacy Linux System

Use OpenSSL 3DES

Command successful

38

Decrypt with Legacy Linux System

Decrypt with OpenSSL

Data recovered

39

Encrypt with Legacy Windows System

Use Windows CryptoAPI

Data encrypted

40

Decrypt with Legacy Windows System

Decrypt with CryptoAPI

Data decrypted

41

Encrypt with Legacy Router

Use 3DES in SNMPv3

Config secured

42

Decrypt with Legacy Router

Read SNMP config

Config decrypted

43

Encrypt with Legacy SCADA System

Use 3DES in control system

Data encrypted

44

Decrypt with Legacy SCADA System

Read control data

Data decrypted

45

Encrypt with Legacy Mobile Device

Use 3DES in old OS

Data encrypted

46

Decrypt with Legacy Mobile Device

Read encrypted data

Data decrypted

47

Encrypt with Legacy Certificate

Use 3DES in PKCS#12

Certificate encrypted

48

Decrypt with Legacy Certificate

Open PKCS#12 file

Certificate readable

49

Encrypt with Legacy Backup Tool

Use 3DES for backup

Backup secured

50

Decrypt with Legacy Backup Tool

Restore backup

Data restored

Being Phased Out - Testcases

#

Test Case

Description

Expected Result

1

Use 3DES in New System

Attempt to use 3DES

Warning or rejection

2

Use AES in New System

Use AES instead

Accepted and preferred

3

Compliance with NIST

Check NIST guidelines

3DES marked as deprecated

4

FIPS 140-3 Validation

Validate 3DES usage

Not recommended

5

TLS Configuration

Enable 3DES cipher suite

Warning or blocked

6

SSH Configuration

Enable 3DES cipher

Deprecated warning

7

VPN Configuration

Use 3DES in IPsec

Warning or fallback to AES

8

Email Encryption

Use 3DES in S/MIME

Deprecated

9

Certificate Encryption

Use 3DES in PKCS#12

Warning issued

10

Java Security Policy

Enable 3DES in JCE

Marked as legacy

11

.NET CryptoConfig

Use 3DES

Warning or fallback

12

OpenSSL Cipher List

Include 3DES

Marked as weak

13

GnuPG Encryption

Use 3DES

Deprecated warning

14

Mobile App Encryption

Use 3DES

Rejected by app stores

15

Web App Encryption

Use 3DES in HTTPS

Browser blocks or warns

16

Cloud Provider Policy

Use 3DES in cloud service

Not allowed or discouraged

17

PCI DSS Compliance

Use 3DES in payment system

Allowed only in legacy systems

18

HIPAA Compliance

Use 3DES for health data

Discouraged

19

GDPR Compliance

Use 3DES for personal data

Not recommended

20

Key Management Policy

Use 3DES keys

Policy flags as legacy

21

Security Audit

Scan for 3DES usage

Flagged as outdated

22

Vulnerability Scan

Scan system using 3DES

Security risk reported

23

Penetration Test

Attack 3DES system

Weaknesses found

24

Brute Force Simulation

Attempt brute force

3DES vulnerable to meet-in-the-middle

25

Performance Benchmark

Compare 3DES vs AES

3DES slower

26

Encryption Library Update

Upgrade crypto library

3DES removed or disabled

27

Legacy System Migration

Migrate from 3DES to AES

Migration successful

28

Legacy System Retention

Keep 3DES for compatibility

Allowed with caution

29

Key Rotation Policy

Rotate 3DES keys

Still flagged as weak

30

Security Policy Review

Review encryption standards

3DES marked for removal

31

Application Hardening

Harden app using 3DES

Not effective

32

Security Training

Educate on 3DES

Marked as deprecated

33

Encryption Algorithm Selection

Choose algorithm

AES preferred over 3DES

34

API Deprecation Notice

Use 3DES API

Deprecation warning shown

35

Code Review

Use 3DES in code

Flagged for replacement

36

Static Code Analysis

Scan for 3DES usage

Security warning

37

Dynamic Analysis

Monitor 3DES usage

Deprecated alert

38

Encryption Policy Enforcement

Enforce AES-only

3DES blocked

39

DevSecOps Pipeline

Include 3DES check

Build fails or warns

40

CI/CD Security Gate

Use 3DES in build

Blocked or flagged

41

Security Documentation

Reference 3DES

Marked as legacy

42

Vendor Security Review

Use 3DES in product

Vendor asked to upgrade

43

Customer Security Requirement

Require AES

3DES not accepted

44

Government Procurement

Use 3DES in proposal

Rejected or flagged

45

Industry Best Practices

Follow OWASP/NIST

3DES discouraged

46

Security Certification

Apply for certification

3DES use questioned

47

Encryption Upgrade Plan

Replace 3DES with AES

Plan approved

48

Legacy Support Window

Allow 3DES temporarily

With strict controls

49

End-of-Life Notice

Vendor announces EOL

3DES removed from roadmap

50

Security Incident Response

Breach in 3DES system

Urgent upgrade to AES recommended

  • Reference links