Security

The mapping is
the crown jewel.

The key that decrypts your token map is returned once, directly to you, and is never stored on the server. A memory dump on its own would be worthless.

Data flow

Where your data goes. And where it never does.

One document, six hops. Real values stay between you and an EU server that forgets them; the model only ever sees tokens.

Youbrowser, extension, MCP client or your code
holds the keysees real values
  • Original document
  • Session key — returned once, only to you
  • Tokens to send on
  • Restored reply
original text
tokens + session key
reply + your key
restored reply
SynonymBratislava, Slovakia
EU hostedGDPRin-memory only
  • Detectors run in memory
  • Token map — encrypted, in memory, TTL
  • Database of your values
  • Training on your content
  • Your key at rest
tokens only
reply with tokens
Model providerChatGPT · Claude · Gemini · your own
your choicetokens only
  • Receives <PERSON_1>, <IBAN_1> …
  • Answers with the same tokens
  • Names, numbers, addresses
  • Your session key
01DetectYour text reaches Synonym over HTTPS and is validated in memory.
02TokeniseTokens and a session key come back. The key is not stored.
03SendOnly tokens go to the model you chose — inside or outside the EU.
04AnswerThe model replies using the same tokens.
05RestoreReply and key return to Synonym; the map is decrypted for that call only.
06ForgetReal values land with you. The map is wiped when the session ends.
EU company, EU hosting, EU law. Synonym s.r.o. is registered in Slovakia; data is processed inside the European Union under the GDPR.
Token lifecycle

The record that empties itself.

One session, then gone. Up to 4 hours on Free, 24 hours on paid plans.

session key valid for 4:00:00
Token map · your sessionduring the session
session_id3f2a91e0…———
secretkQ9x••••••••••••———
<PERSON_1>Ján Novák———
<IBAN_1>SK31 1200 0000 1987 4263 7541———
expires_atin 4 hours———
∅Nothing to recoverthe map, the secret and every value were wiped from memory
No backup, no history, nothing a restart could bring back.
Hosting & data

Where it runs. What we never do.

Plain answers to the questions a security review asks first.

Hosted in the EU

Our infrastructure runs inside the European Union. If you point "Ask the model" at a provider outside the EU, only tokens travel — never the original values.

Your key is never stored

The secret that decrypts your token map is returned once, to you. We keep a hash of API keys, never the key — a full copy of our servers would still restore nothing.

Never used for training

Your content is not used to train models, not sold, and not shared with anyone you didn't choose as a destination. Sub-processors work under a data-processing agreement.

Encrypted in transit, gone at rest

Every request runs over HTTPS. The token map exists only in memory for one session; there is no database table of your values to encrypt, back up or leak.

Need a DPA or the sub-processor list? Write to hello@usesynonym.eu.Details in the Privacy Policy
Certification status

Where each one stands today.

GDPR by design. The rest is in progress — no badges we haven't earned.

GDPRKey stays with you, storage is temporary, no permanent history
Built in
SOC 2 Type IIAudit scope being finalized; controls mapped to the architecture
In progress
ISO 27001ISMS documentation in draft
Planned
HIPAA / BAAProcessing agreement for healthcare organizations and partners
Planned
Planned→ In progress→ Certified

Nothing to leak. Nothing to breach.

Keep using AI on real work — the sensitive part never leaves your side. Set up in minutes, or talk to us about a company-wide rollout.