3DES

The 3DES Cipher (Triple Data Encryption Standard) is a symmetric block cipher that applies the DES algorithm three times to each block of data, significantly increasing security compared to single DES. It operates on fixed-size blocks and uses a key that is internally expanded to 24 bytes. In this implementation, the cipher supports multiple operation modes such as ECB, CBC, CFB, and OFB, along with configurable padding schemes and output formats.

The cipher works by transforming plaintext into ciphertext using a combination of substitution and permutation steps. When encoding, the plaintext is encrypted using the selected mode, key, and padding. When decoding, the same parameters must be used to correctly recover the original message. The output may be represented in Base64 or Hexadecimal, depending on the selected format.

3DES Cipher: Encoding

To encode a message, the plaintext is encrypted using the configured settings. With the default configuration:

• Mode: ECB
• Padding: PKCS7
• Key: b60fb57cc047b6ad14cc7d144f12d34f
• Format: Base64

Encoding the plaintext hello world produces the following result:

Plaintext: hello world
Key:       b60fb57cc047b6ad14cc7d144f12d34f
Mode:      ECB
Padding:   PKCS7

Ciphertext (Base64):
2fENMow8MMBZj9GBTLd3MA==

The plaintext is padded to match the block size, encrypted using Triple DES, and then encoded into Base64 for display.

3DES Cipher: Decoding

To decode, the ciphertext is decrypted using the same configuration. Using the ciphertext above:

Ciphertext: 2fENMow8MMBZj9GBTLd3MA==
Key:        b60fb57cc047b6ad14cc7d144f12d34f
Mode:       ECB
Padding:    PKCS7

Plaintext:
hello world

The Base64 input is first decoded into raw bytes, then decrypted using the Triple DES algorithm. If the key, mode, or padding do not match the original encoding settings, the output will be incorrect or may return an error.

3DES Cipher: Usage Notes

The key is normalized internally to 24 bytes, meaning shorter keys are padded and longer keys are truncated. ECB mode does not use an initialization vector (IV), while other modes such as CBC, CFB, and OFB require one. The initialization vector (IV) must match exactly between encoding and decoding when used. Padding ensures the plaintext fits the required block size; mismatched padding will result in failed decryption. Base64 output is compact and suitable for transport, while hexadecimal provides a raw byte-level representation.

While 3DES was once a widely trusted standard, it has largely been replaced by more modern algorithms such as AES. However, it remains useful for understanding block cipher operation modes, padding schemes, and legacy cryptographic systems.