Slash_Task_1

Text Encryption API — Flask

AES-256-CBC encryption/decryption over a simple REST API.
Every encryption call produces a unique output thanks to a random salt + IV.

Stack

• Flask — web framework
• cryptography — AES-256-CBC + PBKDF2 key derivation (Python stdlib-backed)

Setup

pip install -r requirements.txt
python app.py

Server starts at http://localhost:5000.

---

Endpoints

GET /

Health check.

Response

{ "success": true, "message": "Encryption API is running.", "version": "1.0.0" }

---

POST /encrypt

Encrypt a text string.

Request body

{
  "text": "Hello, world!",
  "passphrase": "my-secret-key"
}

Response

{
  "success": true,
  "token": "abc123...:def456...:ghi789..."
}

The token is base64(salt):base64(iv):base64(ciphertext).
Identical inputs produce different tokens every call.

---

POST /decrypt

Decrypt a token produced by /encrypt.

Request body

{
  "token": "abc123...:def456...:ghi789...",
  "passphrase": "my-secret-key"
}

Response

{
  "success": true,
  "text": "Hello, world!"
}

Error (wrong key)

{
  "success": false,
  "error": "Decryption failed — wrong passphrase or corrupted data."
}

---

cURL Examples

# Encrypt
curl -s -X POST http://localhost:5000/encrypt \
  -H "Content-Type: application/json" \
  -d '{"text":"Hello, world!","passphrase":"my-secret-key"}' | python -m json.tool

# Decrypt (paste token from above)
curl -s -X POST http://localhost:5000/decrypt \
  -H "Content-Type: application/json" \
  -d '{"token":"<paste-token-here>","passphrase":"my-secret-key"}' | python -m json.tool

---

Security Details

Property	Value
Algorithm	AES-256-CBC
Key derivation	PBKDF2-HMAC-SHA256
KDF iterations	100,000
Salt	16 bytes, random per call
IV	16 bytes, random per call
Padding	PKCS7
Token format	base64url(salt):base64url(iv):base64url(ciphertext)

Minimum passphrase length: 8 characters (enforced by the API).