Cipher

Cipher — connector documentation

• MCP endpoint: https://cipher.connectorbay.com/mcp
• REST API: POST https://cipher.connectorbay.com/v1/tools/{tool_name}, described by the OpenAPI 3.1 spec at https://cipher.connectorbay.com/openapi.json
• Transport: Streamable HTTP, stateless, MCP specification 2025-06-18 or later
• Authentication: none required. An optional Authorization: Bearer <key> raises rate limits.
• Health: https://cipher.connectorbay.com/health · Tool schemas: https://cipher.connectorbay.com/tools.json
• Publisher: Unify Dynamics LLC · connectorbay.com/cipher · agent@connectorbay.com

What Cipher is for

Historical and educational cryptography, not a security tool. Cipher implements real, working classical ciphers — the pencil-and-paper systems used from ancient Rome through the 19th century, before modern cryptography existed — so you can actually encode and decode text with them, alongside verified history of who used each one and how it was eventually broken. It's built for puzzles, games, teaching, and curiosity about cryptographic history. It is not suitable for securing real sensitive data, accounts, or communications — use vetted modern cryptography (TLS, AES, a password manager) for anything that actually needs to stay secret.

What it does

Caesar cipher (caesar_cipher) — the oldest cipher with a securely documented historical user: Julius Caesar reportedly used a shift of 3 for military messages, per the Roman historian Suetonius. Encode with any shift (0-25, defaulting to Caesar's own 3), decode with a known shift, or decode with no shift given at all to see all 25 possibilities ranked by frequency analysis. Vigenère cipher (vigenere_cipher) — a polyalphabetic cipher that shifts each letter by an amount from a repeating keyword. Actually first described by Giovan Battista Bellaso in 1553, later misattributed to Blaise de Vigenère; nicknamed "le chiffre indéchiffrable" for resisting cryptanalysis for roughly three centuries until Friedrich Kasiski published a general method to break it in 1863. Atbash (atbash_transform) — one of the oldest known ciphers, reversing the alphabet (A↔Z); attested in the Hebrew Bible. Self-inverse: the same call encodes or decodes. ROT13 (rot13_transform) — a fixed Caesar shift of 13, popularized on Usenet in the early 1980s to hide spoilers and puzzle answers; also self-inverse. Rail fence cipher (rail_fence_cipher) — a transposition cipher that zigzags text across a chosen number of rails and reads it back off, rather than substituting letters. Simple substitution cipher (substitution_cipher) — the general family Caesar and Atbash belong to, mapping every letter through a 26-letter key you supply directly, or a memorable keyword expanded into one the classic way. Frequency analysis (frequency_analysis) — counts letter frequencies in a text and compares them to standard English, the technique first described by the 9th-century polymath Al-Kindi and still the standard way to break a Caesar or simple substitution cipher by hand. Historical background (cipher_info) — verified history for each cipher above, plus the Enigma machine as reference-only context (a WWII electromechanical rotor machine, not a hand-computable cipher, so it has no encode/decode tool here). Glossary (cipher_glossary) — plain definitions of terms like plaintext, ciphertext, key, monoalphabetic, polyalphabetic, cryptanalysis and Kasiski examination.

What it is not

Not a security tool, and not a substitute for one. Every cipher here was broken — often centuries ago — and several (Atbash, ROT13, rail fence) never offered real secrecy even when new. Nothing computed by this connector should be used to protect a password, an account, a real secret, or any sensitive communication. Frequency analysis and the Caesar brute-force ranking are heuristics based on standard English letter frequencies: they work well on a sentence or more of ordinary English and can misfire on short text, other languages, or ciphertext from a polyalphabetic cipher like Vigenère. Historical facts are drawn from public reference sources (Suetonius, David Kahn's The Codebreakers, and Wikipedia) and are accurate as of this connector's build date, not continuously re-verified against new scholarship.

Tools

Encode & decode

caesar_cipher — Caesar (shift) cipher: the oldest cipher with a securely documented historical user — Julius Caesar, per Suetonius, reportedly used a shift of 3 for military messages. Every letter moves a fixed number of places through the alphabet; non-letters are left alone. Use for "caesar cipher shift 7 on hello", "decode this caesar cipher", "brute force this shift cipher". Historical/educational only. Args: text, mode, shift.

vigenere_cipher — Vigenère cipher: a polyalphabetic cipher that shifts each letter by an amount from a repeating keyword instead of one fixed amount, defeating simple frequency analysis. First described by Giovan Battista Bellaso in 1553 (misattributed to Blaise de Vigenère in the 19th century); nicknamed "le chiffre indéchiffrable" for resisting cryptanalysis for roughly three centuries, until Kasiski published a general break in 1863. Use for "vigenere encode ATTACKATDAWN with key LEMON". Historical/educational only. Args: text, key, mode.

atbash_transform — Atbash cipher: one of the oldest known ciphers, reversing the alphabet (A<->Z, B<->Y, ...). Attested in the Hebrew Bible (Jeremiah's "Sheshach" for Babylon). Self-inverse — the same call both encodes and decodes, since applying it twice returns the original text. It has no key at all, so it never offered real secrecy even historically. Use for "atbash this text". Historical/educational only. Args: text.

rot13_transform — ROT13: a Caesar cipher with a fixed shift of 13, popularized on Usenet in the early 1980s to hide spoilers, punchlines and puzzle answers — never intended as real secrecy. Self-inverse — because the alphabet has 26 letters, applying ROT13 twice returns the original text, so the same call both encodes and decodes. Use for "rot13 this joke". Historical/educational only, not a privacy tool. Args: text.

rail_fence_cipher — Rail fence (zigzag) cipher: a transposition cipher that rearranges letters — rather than substituting them — by writing the text in a zigzag across a chosen number of rails and reading it off rail by rail. Weak by design: an attacker just tries every plausible rail count. Use for "rail fence encode with 4 rails", "decode this zigzag cipher, 3 rails". Historical/educational only. Args: text, rails, mode.

substitution_cipher — Simple substitution cipher: the general family Caesar and Atbash both belong to — every letter maps to a different letter via a fixed key, with 26! possible keys. Looks unbreakable at a glance, but falls to frequency analysis (see the frequency_analysis tool), first described by the 9th-century polymath Al-Kindi. Use for "substitution cipher with keyword SECRET", "decode this with key <26 letters>". Historical/educational only. Args: text, key, mode.

Cryptanalysis

frequency_analysis — Counts how often each letter appears in a text and compares it to standard English letter frequencies — the classical cryptanalysis technique first described by the 9th-century Arab polymath Al-Kindi, and still the standard way to attack a Caesar or simple-substitution cipher by hand. Most informative on 50+ letters of ordinary English; not useful against polyalphabetic ciphers like Vigenère. Use for "run frequency analysis on this ciphertext", "what letter shows up most in this text". Historical/educational only. Args: text.

History & glossary

cipher_info — Verified historical background for a named classical cipher: who's credited with it, when, how it works, and (where known) who broke it and how. Includes Enigma as historical context only — it's a WWII-era electromechanical machine, not one of this connector's hand-computable ciphers, so there's no encode/decode tool for it. Use for "who actually invented the vigenere cipher", "history of the caesar cipher", "what was enigma". Args: name.

cipher_glossary — Definitions of common cryptography terms (plaintext, ciphertext, key, cipher, monoalphabetic, polyalphabetic, cryptanalysis, frequency analysis, brute-force attack, Kasiski examination, ...). Use for "what does ciphertext mean", "define frequency analysis". Args: term.

Conventions

• Read-only. Every tool reads public data or computes; nothing is written anywhere and nothing about the user is stored.
• Result envelope. ok: true with data, or ok: false with a structured error (bad_input, not_found, upstream_error). degraded lists optional sources that were unreachable.
• Rate limits. Free tier 60 tool calls/minute and 300/day per user (keyed on the user identifier supplied by the host agent, else client IP); Pro keys raise this. Over-limit calls return HTTP 429 with Retry-After. initialize and tools/list are never counted.

Support

agent@connectorbay.com · connectorbay.com/cipher/support

Cipher — Privacy Policy

Effective 24 September 2026. Unify Dynamics LLC ("we", "us"), Menlo Park, California.

What Cipher is. Cipher is a connector (an MCP server and REST API) that AI assistants and personal agents call on your behalf for classical/historical cipher tools — Caesar, Vigenère, Atbash, ROT13, rail fence and simple substitution encoding/decoding, frequency analysis, cipher history, and a glossary. It is an educational and puzzle/game tool, not a security product — see our Terms of Service. You interact with your assistant; the assistant sends us only the text and key/shift needed for that one calculation.

What we receive. The arguments of each tool call — the text to encode or decode, a shift amount, a Vigenère or substitution key, a cipher or glossary term name — the technical headers needed to serve the request (an IP address or a client identifier supplied by the assistant, and a Pro API key if you have one), and standard server logs.

Everything is computed on our server and nothing is stored. Every cipher tool is a local calculation using the Python standard library; historical background and glossary terms are served from a bundled reference file. No request is forwarded to any third party — there is no upstream call at all — and no text you submit is logged in request bodies, recorded, or used to train anything.

A note on what you paste here. Because these are historical/educational ciphers only, please do not paste anything you actually need to keep secret — a real password, an account number, a private message — into any tool on this connector. It provides no real security, and treating it as if it did would be a mistake regardless of what we do or don't store.

What we do not receive or store. We do not receive your conversation with the assistant, your name, contacts, or account credentials. Rate-limit counters (a client identifier and timestamps) are held in memory for at most 24 hours. Hosting-provider access logs, which contain IP addresses and request paths but not request bodies, are retained for up to 30 days for security and abuse prevention.

Sub-processors. None — every tool is computed locally. Hosting: Vercel (United States regions).

Legal bases and your rights. For users in California, the EU/UK and elsewhere, our processing is necessary to provide the service you request through your assistant. Because we store no personal data beyond short-lived logs, requests to access, correct or delete personal data are usually satisfied automatically; you can still contact agent@connectorbay.com and we will respond within 30 days. We do not sell or share personal information and do not use your data to train models.

Children. Cipher is a general-audience educational tool operated by the adult using the assistant.

Changes. We will post changes here with a new effective date.

Cipher — Terms of Service

Effective 24 September 2026. These terms govern use of the Cipher connector ("the Service") operated by Unify Dynamics LLC ("we", "us").

1. The Service. Cipher returns classical/historical cipher results — Caesar, Vigenère, Atbash, ROT13, rail fence and simple substitution encoding/decoding, frequency analysis, cipher history, and a glossary — computed locally from the Python standard library and a bundled reference file. It is accessed through an AI assistant or directly over MCP or HTTP.
2. Educational tool only — not a security product. Every cipher implemented by the Service is a pencil-and-paper system from before modern cryptography, and every one of them has been broken, in some cases centuries ago; several never offered real secrecy even when new. The Service must not be used, and is not fit, to protect real passwords, accounts, financial information, personal data, or any communication that needs to stay actually secret. Use vetted modern cryptography (e.g. TLS, AES, a reputable password manager) for anything security-critical — never a cipher from this Service.
3. No warranty of historical accuracy. Historical background is drawn from public reference sources believed reliable as of this connector's build date, but is provided for general education, not as scholarly or authoritative certification of any historical claim.
4. Acceptable use. Do not represent output from this Service as providing real confidentiality or security to a third party. Automated use within the published rate limits is welcome.
5. Availability. The Service is provided "as is" without warranty. We may change, limit or discontinue it at any time.
6. Data. Our Privacy Policy describes what we process. In short: your input is answered on our server and nothing is stored.
7. Pro keys. Optional Pro API keys are issued at our discretion, are personal to the holder and may be revoked for abuse.
8. Liability. To the fullest extent permitted by law, Unify Dynamics LLC is not liable for any loss arising from use of or reliance on the Service, including any loss arising from treating a classical cipher as if it provided real security. Our total liability is limited to US $100.
9. Governing law. California law; venue in San Mateo County, California.
10. Contact. Unify Dynamics LLC · agent@connectorbay.com · https://connectorbay.com/cipher

Cipher support

Email agent@connectorbay.com. We answer within two business days.

• MCP endpoint: https://cipher.connectorbay.com/mcp
• REST API: https://cipher.connectorbay.com/openapi.json
• Live status: https://cipher.connectorbay.com/health

When you report a problem, include the question you asked your agent, roughly when, and which agent you used (for example Claude, ChatGPT or Gemini). Never send us passwords, account numbers or ID numbers. Cipher never asks for them.