Android Keystore encryption and decryption

Android Keystore

In this post we will learn how to store a key in android provider keystore and encrypt and decrypt.

Keystore

 KeyStore ks = KeyStore.getInstance("AndroidKeyStore");  
 SecretKey key = new SecretKeySpec(keyByte, alg);  
 KeyStore.SecretKeyEntry secretKeyEntry = new KeyStore.SecretKeyEntry(key);  
   
 // store key in keystore  
 ks.setEntry(  
       "keyName",  
       new KeyStore.SecretKeyEntry(secretKeyEntry.getSecretKey()),  
       new KeyProtection.Builder(KeyProperties.PURPOSE_ENCRYPT | KeyProperties.PURPOSE_DECRYPT)  
          .setBlockModes(KeyProperties.BLOCK_MODE_GCM)  
          .setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_NONE)  
           .build());  
   
 // get key from key store  
 SecretKey keyStoreKey = (SecretKey) ks.getKey("keyName", null);  

Encryption

 Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");  
 cipher.init(Cipher.ENCRYPT_MODE, keyStoreKey);  
 byte[] encryptedByte = cipher.doFinal("Hello World".getByte());  

Decryption

 Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");  
 GCMParameterSpec spec = new GCMParameterSpec(128, cipher.getIV());  
 cipher.init(Cipher.DECRYPT_MODE, keyStoreKey, spec);  
 byte[] decryptedByte = cipher.doFinal(encryptedByte);