Both platforms give you somewhere safe to put a secret, and the two mechanisms are not equivalent. The Android Keystore is primarily a place to hold keys you cannot extract. The iOS keychain is primarily a place to store small secrets you can retrieve. Teams that treat them as the same abstraction end up with a cross-platform design that is weaker on one side than the other.
Short answer
The Android Keystore system is designed so that key material stays inside a container and cannot be extracted from the device, with cryptographic operations performed by the system rather than by your process. Keychain services on Apple platforms store small pieces of sensitive data such as passwords and tokens, protected by access control and returned to your app when the conditions are met. The distinction is extraction: Keystore is built around keys you use without seeing, while keychain is built around items you retrieve.
What the Android Keystore gives you
The core property is that key material is generated in and never leaves a protected container. Your app asks for a signature or a decryption; the system performs it and returns the result. On devices with the appropriate hardware, that container is backed by a secure element or a trusted execution environment.
Keys can carry requirements attached at generation time. A key can be marked as requiring user authentication before use, invalidated when the enrolled biometric set changes, restricted to a single purpose, or bound to a particular padding and block mode. Those constraints are enforced by the system rather than by your code, which is the entire point.
What the Keystore is not is a general-purpose store for arbitrary secrets. Putting a refresh token directly into it is not the intended shape. The intended shape is a Keystore key that encrypts the token, with the ciphertext stored in ordinary app storage.
That indirection catches people, because it means a well-designed Android implementation has two artifacts where iOS has one. It is also what makes the Android design strong: the token at rest is useless without a key that cannot be exported.
What the iOS keychain gives you
The keychain stores items and returns them, which makes it a more direct fit for tokens, passwords and small secrets.
Each item carries an accessibility attribute controlling when it can be read, and this is the setting that most often goes wrong. An item readable once the device has been opened after a restart behaves very differently from one that requires the device to be open at that moment, and the most permissive settings allow reading in states where the user is not present.
Items can also carry an access control object requiring biometry or the device credential before the item is returned. That is the iOS equivalent of an authentication-required Keystore key, and it is what turns keychain storage into a real control rather than a convenient place to put a string.
The keychain also has behaviour around backup and device transfer that has to be chosen deliberately. Items can be excluded from backups by using a this-device-only accessibility class, which is usually correct for credentials and usually wrong for data the user would expect to survive a device migration.
Where the two designs diverge in practice
Extraction. On Android the strong pattern hides the key permanently. On iOS the strong pattern hides the item behind an access control but returns it once satisfied. Both are defensible; they fail differently.
Granularity. Keychain accessibility is per item and easy to get subtly wrong across a large codebase. Keystore constraints are per key and set once at generation, which makes them harder to change later and harder to weaken by accident.
Invalidation. Both platforms can invalidate on biometric enrollment change, and the Android version is more commonly used because it is a generation-time flag rather than a policy decision at read time.
Availability. Keystore hardware backing varies by device, and an app that requires it needs a defined path for devices that lack it. Apple's hardware is more uniform, which removes a class of decision from iOS engineering.
Backup and migration. Keychain items can travel with a backup unless you say otherwise. Hardware-backed Keystore keys cannot migrate at all, which means a restored Android device always requires re-authentication.
Designing one flow for both platforms
The shared abstraction that works is a credential envelope rather than a storage location.
Define the operation, not the storage. Your app needs to seal a refresh credential and unseal it after user authentication. On Android that is a Keystore key with authentication required, encrypting a blob you keep in app storage. On iOS that is a keychain item with a biometry-backed access control. The interface your application code sees is identical; the implementations are genuinely different.
Do not paper over the invalidation differences. If the Android key invalidates on enrollment change and the iOS item does not, you have shipped two different security postures under one feature name, and the one you describe in your documentation will be whichever you implemented first.
And write down the accessibility class you chose on iOS and the key parameters you chose on Android, next to each other, so that a future change on one platform is visibly a change on only one platform.
The mistakes that show up in a built app
Storing a token as a plain string in shared preferences on Android while using the keychain properly on iOS. This is the most common cross-platform asymmetry and it usually comes from an Android implementation written under time pressure.
Choosing the most permissive keychain accessibility because a background refresh failed once. The fix for a background task that cannot read a credential is usually to restructure when the refresh happens, not to make the credential readable while the device is locked.
Generating a Keystore key without authentication requirements and then gating its use with an application-level check, which moves enforcement out of the system and back into patchable code.
Assuming hardware backing exists. Key generation can fall back in ways that change the guarantee, and an app that never checks has a security property it cannot describe accurately.
These are visible in a built artifact, which is why an artifact-level pass is worth running on both platform builds rather than reasoning about the source. A scanner such as PTKD.com will surface credentials in unprotected storage and permissive keychain configuration, which covers the majority of what goes wrong here in practice.
The MASVS storage category and the cryptography category describe the requirements these implementations are meant to satisfy, and Android's own security best practices cover the platform-specific side.
Cross-platform frameworks, where this gets worse
React Native, Flutter and similar frameworks introduce a layer between your code and both platform stores, and that layer is where cross-platform storage guarantees quietly diverge.
The common pattern is a storage plugin presenting one interface for both platforms. What matters is what it maps to underneath. Some map to the keychain on iOS and to encrypted preferences on Android with a Keystore-backed key, which is a sound design. Others map to the keychain on one side and to plain preferences on the other, which is the asymmetry described above shipped as a dependency.
Read the plugin's implementation rather than its description. The README describes intent; the platform-specific source describes behaviour, and the two do not always agree, particularly in plugins that added Android support later.
Check what happens when hardware backing is unavailable. A plugin that silently falls back to weaker storage on devices without a secure element has made a decision for you, and it is not visible from your application code.
And check whether the plugin sets an accessibility attribute at all on iOS, since an unspecified value takes a platform default rather than the restrictive value you would have chosen.
Migrating storage without locking users out
Changing where a credential lives is a migration, and the failure mode is a silent logout for everyone on the old scheme.
Read from the old location and write to the new one on first launch after the update, then delete the old copy. Skipping the delete is the most common error, since it leaves the weaker copy in place indefinitely and the migration achieves nothing.
Handle the case where the new write fails. On Android, key generation can fail on unusual devices; on iOS, an access control requiring biometry fails when nothing is enrolled. Both need a defined fallback rather than an exception that logs the user out.
And keep the migration code for at least two release cycles, because users skip updates and a device that jumps three versions still needs the path.
Testing storage decisions
The verification is mechanical and it is worth doing once per platform rather than trusting the implementation.
On Android, pull the app's data directory from a debug build and read what is there. Credentials that appear in plain form in shared preferences or a database file are the finding, and they are visible in seconds.
On iOS, inspect the keychain item attributes rather than only checking that a read succeeds, because a successful read tells you nothing about the accessibility class that permitted it.
On both, test with the device locked, after a restart before any authentication, and after a restore to a different device. Those three states are where the accessibility and migration decisions actually show themselves, and they are all easy to skip in normal testing.
Documenting the guarantee you actually provide
The last step is writing down what your storage design promises, in a sentence a support engineer or a customer's security reviewer could read.
Something like: credentials are held encrypted with a hardware-backed key requiring user authentication, are not included in device backups, and do not survive a transfer to a new device. That sentence is checkable, it is specific to what you implemented, and it is the answer to most security questionnaires you will receive.
Vague statements are what get teams into trouble here. Claiming that data is encrypted on the device is true of almost every app, since the platform encrypts storage at rest anyway, and it says nothing about whether your credential is protected from someone holding an opened device.
Write the sentence per platform if the platforms differ, and treat a difference you cannot justify as a defect rather than as a note.
The question that settles most arguments
When a team disagrees about whether a storage choice is good enough, one question resolves it faster than a standards discussion.
If someone picks up this phone, opened, with no passcode prompt in the way, what can they get?
That framing removes the abstraction. An item readable whenever the device is open is readable by the person holding an open device. An item requiring biometry is not. A Keystore key requiring authentication is not. Plain preferences are readable by anyone with a debug connection whether the device is open or not.
Most storage decisions become obvious once phrased that way, and the ones that stay contested are usually about how much friction the product can tolerate rather than about what the platform provides.
What to take away
Keystore is about keys you cannot extract; keychain is about items you can retrieve under conditions. Design to the difference rather than to a shared mental model.
On Android, encrypt the secret with a Keystore key and store the ciphertext, rather than trying to put the secret in the Keystore directly.
On iOS, the accessibility attribute is the setting that matters most, and the permissive values are chosen for the wrong reasons more often than any other security parameter.
Attach authentication requirements at key generation and access control creation, so the system enforces them instead of your control flow.
And check both platform builds, because cross-platform teams reliably end up with one implementation weaker than the other, and it is usually not the one anyone remembers writing.
