Caesar Cipher is one of the simplest and most widely known encryption techniques. It's a substitution cipher where each letter in the plaintext is shifted a certain number of places down or up the alphabet. For example, with a shift of 3, A becomes D, B becomes E, and so on. This tool uses the same principle to encrypt and decrypt your text.

No, Caesar Cipher is not secure for modern encryption needs. It's easily broken through frequency analysis or brute force attacks since there are only 25 possible keys. This tool is primarily for educational purposes, learning cryptography basics, or simple obfuscation. For real security, use modern encryption algorithms like AES.

The key can be any number from 1 to 25. For basic use, keys between 3 and 13 are commonly used. Remember that both the sender and receiver need to use the same key. For slightly better security, avoid obvious keys like 1, 13, or 25. The security doesn't significantly improve with different keys since all 25 possibilities can be easily tested.

This Caesar Cipher implementation only encrypts alphabetical characters (A-Z, a-z). Numbers, symbols, spaces, and punctuation marks remain unchanged. This is because the cipher only shifts letters within the alphabet. For full text encryption including special characters, more advanced encryption methods are needed.

We strongly recommend NOT using this tool for sensitive, personal, or confidential information. Caesar Cipher provides minimal security and can be easily decrypted by anyone. This tool is best used for learning cryptography concepts, simple puzzles, or casual message obfuscation where real security is not required.