Some vault apps hide files from view. Some put a PIN in front of them. ArkWarden encrypts them. These pages show exactly what each approach means in practice.
Apple's Hidden Album moves photos out of view but does not encrypt them. The files remain in the Photos library, sync to iCloud, and are accessible to anyone who knows your passcode.
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Private Photo Vault protects photos with a PIN. AES-256 encryption applies to their Cloud Vault backup only. Local files are PIN-protected, not individually encrypted.
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Keepsafe encrypts files on your device, but by its own admission is not a zero-knowledge app. It requires an account and an email address, and can view or share your data in specific cases.
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Calculator# hides files with a disguised calculator icon and a password. Its own listing does not name an encryption method. ArkWarden encrypts every file with a key derived from your pattern.
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SPV Photo Vault controls access with a PIN and never names an encryption method in its own description. ArkWarden encrypts every file with a key derived from your pattern.
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LockMyPix encrypts files with AES-CTR 256, a real named method. Its optional email recovery depends on their servers. ArkWarden has no account, no email, and no server under any configuration.
Read the comparisonEvery file encrypted on your device. No account, no ads, no server. Your pattern is the key.
Read how the encryption works