Build Your Own Cipher Sandbox

Design, test, and analyze custom ciphers by chaining substitution (confusion) and permutation (diffusion) layers. Observe state evolutions step-by-step, verify invertibility, and calculate avalanche metrics in real-time.

Cipher Template Presets

Rounds:

Pipeline Stages (3)

Stage 1 • substitution

S-Box Layer (Substitution)

Shift Amount:

Stage 2 • permutation

P-Box Layer (Permutation)

Block Size:

Permutation Array (comma separated):

Stage 3 • substitution

Round Key XOR

XOR Key String:

Input Text (encrypt)

Output Result (0.81 ms)

GJ2<EB3-VC02

Round 1 — S-Box Layer (Substitution)SUBSTITUTION (caesar)

IN:CRYPTOGRAPHY

OUT:HWDUYTLWFUMD

Caesar Shift: +5 positions

Round 1 — P-Box Layer (Permutation)PERMUTATION (pbox)

IN:HWDUYTLWFUMD

OUT:DHUWLYWTMFDU

P-Box Permutation (Forward block mapping [2, 0, 3, 1])

Round 1 — Round Key XORSUBSTITUTION (xor)

IN:DHUWLYWTMFDU

OUT: fed

XOR Layer: Bitwise XOR with key "KEY1"

Round 2 — S-Box Layer (Substitution)SUBSTITUTION (caesar)

IN: fed

OUT: kji

Caesar Shift: +5 positions

Round 2 — P-Box Layer (Permutation)PERMUTATION (pbox)

IN: kji

OUT:k ji

P-Box Permutation (Forward block mapping [2, 0, 3, 1])

Round 2 — Round Key XORSUBSTITUTION (xor)

IN:k ji

OUT:GJ2<EB3-VC02

XOR Layer: Bitwise XOR with key "KEY1"

Understanding Substitution & Permutation Networks

Claude Shannon identified two primary fundamental principles that modern block ciphers rely on to thwart cryptanalysis:

Substitution (Confusion)

Substitution layers map plaintext units to ciphertext units, masking the mathematical relationship between the secret key and the ciphertext. Examples include S-Boxes, Caesar shifts, Affine transforms, and XOR layers.

Permutation (Diffusion)

Permutation layers reorder character or bit positions across the state, spreading statistical structure of the input across the output. Examples include P-Boxes, columnar transpositions, block swaps, and cyclic shifts.

Multi-Round Iteration

A single substitution or permutation layer is easily broken. Modern block ciphers like AES and DES repeat alternating substitution-permutation rounds to achieve optimal Avalanche Effect (flipping 1 bit changes ~50% of output bits).