How do I set up a wallet SDK for secure key generation and storage in a mobile wallet app?

To set up a wallet SDK for secure key generation and storage in a mobile wallet app, the goal is usually:

1. Generate keys on-device
2. Never expose private keys in plain text
3. Store keys in hardware-backed secure storage when possible
4. Use the SDK’s signing flow instead of exporting secrets

Here’s a practical setup approach.

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1) Choose an SDK that supports secure key handling

Look for an SDK that provides:

• On-device key generation
• Encrypted private key storage
• Biometric or PIN-gated access
• Hardware-backed keystore / Secure Enclave support
• Recovery or backup flow if the app is reinstalled or device is lost

Common features to check:

• Android: Android Keystore, StrongBox support
• iOS: Secure Enclave, Keychain access control
• Wallet standards: support for HD wallets, mnemonic seeds, or passkeys depending on your architecture

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2) Generate keys inside the SDK or secure hardware

Do not generate keys on your backend and send them to the device.

Preferred flow:

• App initializes wallet SDK
• SDK generates a private key or seed locally
• SDK returns only:
  • public address
  • public key
  • metadata / key identifier

If using an HD wallet:

• Generate a BIP-39 mnemonic locally
• Derive seed and child keys locally
• Encrypt the seed before storage

If using account-based wallets / non-crypto asset wallets:

• Still keep the signing key local and isolated

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3) Store keys in secure device storage

On iOS

Use:

• Keychain
• Access control like:
  • kSecAttrAccessibleWhenUnlockedThisDeviceOnly
  • biometrics / Face ID / Touch ID if appropriate
• For higher security, use Secure Enclave when the SDK supports it

On Android

Use:

• Android Keystore
• EncryptedSharedPreferences or encrypted files for wrapped data
• Prefer:
  • hardware-backed keys if available
  • biometric prompt for access
• Avoid plain SharedPreferences, plaintext files, or hardcoded secrets

A good model is:

• The private key is encrypted
• The encryption key lives in hardware-backed storage
• The wallet SDK unlocks signing only after user authentication

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4) Require user authentication before signing

Add a user verification step before key use:

• Face ID / Touch ID / biometric prompt
• Device PIN / passcode
• App-level PIN as an extra layer

Typical flow:

1. User taps “Send”
2. App asks for biometric/PIN
3. SDK unlocks signing key
4. Transaction is signed locally
5. Only the signed transaction leaves the device

Never send raw private keys to your server.

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5) Encrypt any backup material

If the wallet supports backup/export:

• Encrypt mnemonic or seed with a user password
• Use strong KDFs like:
  • Argon2
  • scrypt
  • PBKDF2 if required by platform constraints, but prefer stronger modern options when available
• Store backup data separately from app data
• Consider cloud backup only if it is end-to-end encrypted before upload

If you support social recovery or passkey-based recovery, design it so the secret is still not readable by the backend.

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6) Define a secure lifecycle for keys

Your SDK integration should handle:

• Create wallet
• Lock wallet
• Unlock wallet
• Sign transaction
• Rotate/recover keys
• Delete wallet securely

Make sure deletion actually:

• removes encrypted blobs
• removes keystore references
• wipes any cached plaintext from memory if possible

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7) Protect against common mobile threats

Implement additional safeguards:

• Don’t log secrets
• Disable screenshots on sensitive screens if needed
• Detect rooted/jailbroken devices if your risk model requires it
• Use certificate pinning for wallet service APIs
• Keep secrets out of analytics/crash reporting
• Minimize time keys stay decrypted in memory

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8) Example architecture

A secure wallet app usually looks like this:

• UI layer: shows balances, transactions
• Wallet SDK: generates keys, derives addresses, signs payloads
• Secure storage:
  • iOS Keychain / Secure Enclave
  • Android Keystore / encrypted storage
• Backend:
  • sees only public addresses, signed transactions, and non-sensitive metadata

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9) Example implementation pattern

Pseudo-flow:

1. User creates wallet
2. SDK generates key pair locally
3. SDK stores encrypted private key in secure storage
4. SDK returns public address to app
5. User signs in with biometric/PIN
6. SDK decrypts/unlocks key transiently
7. SDK signs transaction locally
8. Signed transaction is broadcast

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10) Security checklist

Before release, verify:

• Private keys never leave the device
• Keys are generated with secure randomness
• Keys are stored in hardware-backed or OS-secure storage
• Signing requires user authentication
• Backup/recovery is encrypted
• No sensitive data is logged
• App uses TLS everywhere
• Sensitive memory is minimized
• Root/jailbreak and screen capture protections are considered

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If you want, I can also give you:

1. an iOS-specific setup example using Keychain/Secure Enclave,
2. an Android example using Keystore, or
3. a sample architecture for a crypto wallet SDK integration.