Package com.microej.crypto.test.util

Class CipherAssertions

java.lang.Object

com.microej.crypto.test.util.CipherAssertions

public final class CipherAssertions
extends java.lang.Object

Assertions on Cipher shared by the cipher test classes.

Method Summary

Modifier and Type	Method	Description
static void	assertIvRoundTrips(java.lang.String transformation, java.lang.String keyAlgorithm, byte[] key, byte[] plaintext, int expectedIvLength)	Asserts that a cipher initialized without parameters generates an initialization vector, returns it from Cipher.getIV() with the expected length, and that decrypting with that vector gives the plaintext back.
static void	assertReinitMatchesFreshCipher(java.lang.String transformation, java.lang.String keyAlgorithm, byte[] firstKey, java.security.spec.AlgorithmParameterSpec firstParameters, byte[] secondKey, java.security.spec.AlgorithmParameterSpec secondParameters, byte[] plaintext)	Asserts that a cipher initialized, fed one block, then initialized again with another key and other parameters encrypts as a freshly created cipher does, and that the result decrypts.
static void	assertRoundTripAtOffsets(java.lang.String label, javax.crypto.Cipher encryptor, javax.crypto.Cipher decryptor, byte[] plaintext, byte[] ciphertextAtZero)	Asserts that encrypting from a sub-range into an offset produces the given ciphertext, that decrypting it back from a sub-range into an offset gives the plaintext, and that neither operation touches the bytes around its result.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

assertIvRoundTrips

public static void assertIvRoundTrips(java.lang.String transformation,
                                      java.lang.String keyAlgorithm,
                                      byte[] key,
                                      byte[] plaintext,
                                      int expectedIvLength)
                               throws java.security.GeneralSecurityException

Asserts that a cipher initialized without parameters generates an initialization vector, returns it from Cipher.getIV() with the expected length, and that decrypting with that vector gives the plaintext back.

The round trip is what shows the value returned is the value actually used.

Parameters:

transformation - the transformation, with a mode that takes an initialization vector

keyAlgorithm - the algorithm of the key

key - the raw key

plaintext - the plaintext, a whole number of blocks when the transformation has no padding

expectedIvLength - the length in bytes of the initialization vector the transformation implies

Throws:

java.security.GeneralSecurityException - if the transformation or the key is rejected

assertRoundTripAtOffsets

public static void assertRoundTripAtOffsets(java.lang.String label,
                                            javax.crypto.Cipher encryptor,
                                            javax.crypto.Cipher decryptor,
                                            byte[] plaintext,
                                            byte[] ciphertextAtZero)
                                     throws java.security.GeneralSecurityException

Asserts that encrypting from a sub-range into an offset produces the given ciphertext, that decrypting it back from a sub-range into an offset gives the plaintext, and that neither operation touches the bytes around its result.

The expected ciphertext is the one of the same operation at offset zero, so the assertion holds for every mode without a written-out vector per transformation. Each output is sized from Cipher.getOutputSize(int): a backend may require more room than it writes and reject a smaller array before it writes anything. The simulator mock does not, so a size taken from the result is only caught on a target.

Parameters:

label - the transformation, for the assertion messages

encryptor - an initialized encrypting cipher, with its additional authenticated data already supplied when it takes some

decryptor - an initialized decrypting cipher, with the same additional authenticated data

plaintext - the plaintext, a whole number of blocks when the transformation has no padding

ciphertextAtZero - the ciphertext of the same operation at offset zero

Throws:

java.security.GeneralSecurityException - if an operation is rejected

assertReinitMatchesFreshCipher

public static void assertReinitMatchesFreshCipher(java.lang.String transformation,
                                                  java.lang.String keyAlgorithm,
                                                  byte[] firstKey,
                                                  java.security.spec.AlgorithmParameterSpec firstParameters,
                                                  byte[] secondKey,
                                                  java.security.spec.AlgorithmParameterSpec secondParameters,
                                                  byte[] plaintext)
                                           throws java.security.GeneralSecurityException

Asserts that a cipher initialized, fed one block, then initialized again with another key and other parameters encrypts as a freshly created cipher does, and that the result decrypts.

A second initialization is how an application reaches the backend's cipher-close path: the context of the first initialization has to be released before the second one is allocated. Releasing too late leaks, releasing too early leaves the second context using freed memory. The data fed to the first context is never finalized: the second initialization abandons a context that holds data, and additional authenticated data on an authenticated mode, which is the harder case for a backend to release. A second context built on the remains of the first fails the comparison with the fresh cipher.

Parameters:

transformation - the transformation

keyAlgorithm - the algorithm of the keys

firstKey - the raw key of the first initialization

firstParameters - the parameters of the first initialization

secondKey - the raw key of the second initialization

secondParameters - the parameters of the second initialization, which must differ from the first ones on an authenticated mode

plaintext - the plaintext, a whole number of blocks when the transformation has no padding

Throws:

java.security.GeneralSecurityException - if the transformation, a key or a parameter is rejected