A basic example of how to perform symmetric key encryption/decryption using AES and Java's cryptography API.
CryptoHelper.java
importjava.security.Key; |
importjava.security.SecureRandom; |
importjavax.crypto.Cipher; |
importjavax.crypto.KeyGenerator; |
importjavax.crypto.SecretKey; |
importjavax.crypto.spec.IvParameterSpec; |
importorg.apache.commons.codec.binary.Base64; |
publicclassCryptoHelper { |
publicstaticvoidmain( String [] args ) throwsException { |
CryptoHelper crypto =newCryptoHelper(); |
String plaintext ='This is a good secret.'; |
System.out.println( plaintext ); |
String ciphertext = crypto.encrypt( plaintext ); |
System.out.println( ciphertext ); |
String decrypted = crypto.decrypt( ciphertext ); |
System.out.println( decrypted ); |
} |
publicStringencrypt( Stringplaintext ) throwsException { |
return encrypt( generateIV(), plaintext ); |
} |
publicStringencrypt( byte [] iv, Stringplaintext ) throwsException { |
byte [] decrypted = plaintext.getBytes(); |
byte [] encrypted = encrypt( iv, decrypted ); |
StringBuilder ciphertext =newStringBuilder(); |
ciphertext.append( Base64.encodeBase64String( iv ) ); |
ciphertext.append( ':' ); |
ciphertext.append( Base64.encodeBase64String( encrypted ) ); |
return ciphertext.toString(); |
} |
publicStringdecrypt( Stringciphertext ) throwsException { |
String [] parts = ciphertext.split( ':' ); |
byte [] iv =Base64.decodeBase64( parts[0] ); |
byte [] encrypted =Base64.decodeBase64( parts[1] ); |
byte [] decrypted = decrypt( iv, encrypted ); |
returnnewString( decrypted ); |
} |
privateKey key; |
publicCryptoHelper( Keykey ) { |
this.key = key; |
} |
publicCryptoHelper() throwsException { |
this( generateSymmetricKey() ); |
} |
publicKeygetKey() { |
return key; |
} |
publicvoidsetKey( Keykey ) { |
this.key = key; |
} |
publicstaticbyte [] generateIV() { |
SecureRandom random =newSecureRandom(); |
byte [] iv =newbyte [16]; |
random.nextBytes( iv ); |
return iv; |
} |
publicstaticKeygenerateSymmetricKey() throwsException { |
KeyGenerator generator =KeyGenerator.getInstance( 'AES' ); |
SecretKey key = generator.generateKey(); |
return key; |
} |
publicbyte [] encrypt( byte [] iv, byte [] plaintext ) throwsException { |
Cipher cipher =Cipher.getInstance( key.getAlgorithm() +'/CBC/PKCS5Padding' ); |
cipher.init( Cipher.ENCRYPT_MODE, key, newIvParameterSpec( iv ) ); |
return cipher.doFinal( plaintext ); |
} |
publicbyte [] decrypt( byte [] iv, byte [] ciphertext ) throwsException { |
Cipher cipher =Cipher.getInstance( key.getAlgorithm() +'/CBC/PKCS5Padding' ); |
cipher.init( Cipher.DECRYPT_MODE, key, newIvParameterSpec( iv ) ); |
return cipher.doFinal( ciphertext ); |
} |
} |
commented Dec 25, 2017
Thank you! Thanks to you, I could do this. |
commented Mar 8, 2018
The key and IVs must be cryptographically secure random numbers, don't just type them and don't use C#'s Random function. The size of the key and the IV depend on the cipher algorithm used, and can be accessed by the properties on the classes. To generate a CSRPNG you do something like. Many Git servers authenticate using SSH public keys. In order to provide a public key, each user in your system must generate one if they don’t already have one. This process is similar across all operating systems. First, you should check to make sure you don’t already have a key. Aug 27, 2019 Using symmetric key or using the developers gpg key. Symmetric Key. First we will create the symmetric key(and lets name it as secret-file-to-unlock) using the command, git-crypt export-key secret-file-to-unlock. Then share the symmetric key with the developers securely using gpg or any other means. $ git-crypt init This will generate a symmetric key for. In addition to the implicit default key, git-crypt supports alternative keys which can be used to encrypt.
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