Encrypted SIM cards: what a SIM encrypts and what it can't

What is an encrypted SIM card?

Every SIM is already encrypted in one sense: it holds a secret key, shared with your mobile operator, that proves your subscription is real and helps encrypt traffic between your phone and the network's equipment.

That link encryption protects your traffic over the air, between the handset and the mast. The GSMA, the mobile industry body, lists encryption on the radio path between phone and base station as a 4G security feature. 5G goes further. The phone can conceal its permanent subscriber identity using a value called the SUCI, so the identity is not sent in the clear over the radio. The GSMA notes that the full set of 5G protections depends on operators moving to a 5G core network, so not every 5G connection has them yet.

An eSIM works the same way. It holds the same kind of operator identity and keys as a plastic SIM; it is downloaded rather than inserted.

When a product is marketed as an encrypted SIM card, the seller usually means something more: extra privacy features bundled on top. That claim is worth testing, because of what a SIM cannot do.

Does a SIM encrypt your calls and texts?

Only between your phone and the network. After that, your operator's systems handle the call or message, so the SIM does not keep your content private from the network itself.

Text messages are the weakest point. CISA, the US cybersecurity agency, says plainly that SMS messages are not encrypted, and recommends end-to-end encrypted apps instead. End-to-end encryption runs on the devices at each end of a conversation. That is why no SIM, however it is marketed, can provide it alone.

Is there a best encrypted SIM card?

Not in the sense most buyers hope for. No SIM can make your conversations private alone, so the best choice is the one whose claims you can check.

Before paying for any SIM sold as encrypted, ask the seller these four questions.

• What exactly is encrypted, and between which two points?
• Who holds the keys: you, or the seller?
• Has the design been independently audited, and is the report public?
• What records does the seller keep, and does it ask for ID?

Can a SIM card be hacked?

Yes, SIMs have had real weaknesses, so treat a SIM as one component rather than a sealed vault.

In 2013, security researcher Karsten Nohl showed that some SIMs still protected over-the-air management messages with outdated DES keys, which he could crack to take control of the card. Vague answers to the questions above are a reason to walk away from any seller.

What is the most secure SIM card setup?

The account and settings around the SIM matter more than the card itself: protect your carrier account, lock the SIM with a PIN, and stop relying on text-message codes.

• Guard against SIM swapping. In a SIM swap, someone convinces your carrier to move your number onto their SIM. CISA advises adding a PIN and multi-factor authentication to your carrier account. In the US, FCC rules adopted on 15 November 2023 require carriers to use secure methods to authenticate a customer before moving a number to a new device or provider.
• Set a SIM PIN. Apple explains that a SIM PIN stops other people using your SIM or eSIM for calls or data. Choose it carefully: too many wrong guesses can lock the SIM permanently, and you would need a replacement.
• Drop SMS codes where you can. CISA recommends against using SMS as a second factor, because it is not phishing-resistant. Use an authenticator app or a passkey instead.
• Consider an eSIM. An eSIM cannot be pulled out of the phone and swapped in seconds. That blocks one kind of physical tampering, but it will not stop a SIM swap carried out through your account.

Where does a no-ID eSIM fit?

It solves a different problem: it keeps your name out of the provider's records. It adds no encryption beyond what every network and website already uses.

MoneroSIM sells data-only eSIMs with no ID check and no account, paid with Monero, Bitcoin, Lightning, USDT or card (see paying for an eSIM with crypto). Our FAQ is clear about the limits: traffic is encrypted between your device and the sites you visit, exactly as on any other network. Because the eSIM is data only, it has no phone number for anyone to port away.

Pair it with an end-to-end encrypted messaging app if you need private conversations. To see what anonymous does and does not cover, read our anonymous eSIM page.

Encrypted SIM card FAQ

In short, a SIM protects your connection to the network, not the contents of your messages.

Can you encrypt a SIM card yourself? Not its built-in cryptography, which your operator controls. What you can do is lock the SIM or eSIM with a SIM PIN.

Is an eSIM more secure than a physical SIM? It is different rather than safer overall. An eSIM cannot be removed in seconds, but both depend equally on how well your carrier account is protected.

Does 5G encrypt more than 4G? It protects more of your identity. 5G can hide the permanent subscriber identity using the SUCI, where the operator runs a 5G core network.

Will an encrypted SIM card hide my location? No. Like any SIM, it connects through the network's cells, so the network still knows roughly where the phone is.