How to encrypt and decrypt file in Android

Question

I want to encrypt file and store it in SD card  I want to decrypt that encrypted file and store it in SD card again  I have tried to encrypt file by opening it as file stream and encrypt it but it is not working  I want some idea on how to do this

User · Answer

You could use java-aes-crypto or Facebook's Conceal

java-aes-crypto

Quoting from the repo

A simple Android class for encrypting & decrypting strings, aiming to avoid the classic mistakes that most such classes suffer from.

Facebook's conceal

Quoting from the repo

Conceal provides easy Android APIs for performing fast encryption and authentication of data

User · Answer

I had a similar problem and for encrypt decrypt i came up with this solution   public static byte   generateKey String password  throws Exception       byte   keyStart   password getBytes  UTF-8         KeyGenerator kgen   KeyGenerator getInstance  AES        SecureRandom sr   SecureRandom getInstance  SHA1PRNG    Crypto        sr setSeed keyStart       kgen init 128  sr       SecretKey skey   kgen generateKey        return skey getEncoded       public static byte   encodeFile byte   key  byte   fileData  throws Exception        SecretKeySpec skeySpec   new SecretKeySpec key   AES        Cipher cipher   Cipher getInstance  AES        cipher init Cipher ENCRYPT MODE  skeySpec       byte   encrypted   cipher doFinal fileData        return encrypted     public static byte   decodeFile byte   key  byte   fileData  throws Exception       SecretKeySpec skeySpec   new SecretKeySpec key   AES        Cipher cipher   Cipher getInstance  AES        cipher init Cipher DECRYPT MODE  skeySpec        byte   decrypted   cipher doFinal fileData        return decrypted      To save a encrypted file to sd do   File file   new File Environment getExternalStorageDirectory     File separator    your folder on sd    file name    BufferedOutputStream bos   new BufferedOutputStream new FileOutputStream file    byte   yourKey   generateKey  password    byte   filesBytes   encodeFile yourKey  yourByteArrayContainigDataToEncrypt   bos write fileBytes   bos flush    bos close      To decode a file use   byte   yourKey   generateKey  password    byte   decodedData   decodeFile yourKey  bytesOfYourFile     For reading in a file to a byte Array there a different way out there  A Example  http   examples javacodegeeks com core-java io fileinputstream read-file-in-byte-array-with-fileinputstream

User · Answer

Use a CipherOutputStream or CipherInputStream with a Cipher and your FileInputStream   FileOutputStream   I would suggest something like Cipher getInstance  AES CBC PKCS5Padding   for creating the Cipher class  CBC mode is secure and does not have the vulnerabilities of ECB mode for non-random plaintexts  It should be present in any generic cryptographic library  ensuring high compatibility   Don t forget to use a Initialization Vector  IV  generated by a secure random generator if you want to encrypt multiple files with the same key   You can prefix the plain IV at the start of the ciphertext  It is always exactly one block  16 bytes  in size   If you want to use a password  please make sure you do use a good key derivation mechanism  look up password based encryption or password based key derivation   PBKDF2 is the most commonly used Password Based Key Derivation scheme and it is present in most Java runtimes  including Android  Note that SHA-1 is a bit outdated hash function  but it should be fine in PBKDF2  and does currently present the most compatible option    Always specify the character encoding when encoding decoding strings  or you ll be in trouble when the platform encoding differs from the previous one  In other words  don t use String getBytes   but use String getBytes StandardCharsets UTF 8    To make it more secure  please add cryptographic integrity and authenticity by adding a secure checksum  MAC or HMAC  over the ciphertext and IV  preferably using a different key  Without an authentication tag the ciphertext may be changed in such a way that the change cannot be detected   Be warned that CipherInputStream may not report BadPaddingException  this includes BadPaddingException generated for authenticated ciphers such as GCM  This would make the streams incompatible and insecure for these kind of authenticated ciphers

[android] How to encrypt and decrypt file in Android?

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