Java IO.pdf - Nguyen Dang Binh

public static final Cipher getInstance(String transformation)
throws NoSuchAlgorithmException, NoSuchPaddingException
public static final Cipher getInstance(String transformation, String
provider)
throws NoSuchAlgorithmException, NoSuchProviderException,
NoSuchPaddingException
Java I/O
The first argument, transformation, is a string that names the algorithm, mode, and padding
scheme to be used to encrypt or decrypt the data. Examples include "DES",
"PBEWithMD5AndDES", and "DES/ECB/PKCS5Padding". The optional second argument to
getInstance(), provider, names the preferred provider for the requested transformation. If
more than one installed provider supports the transformation, the one named in the second
argument will be used. Otherwise, an implementation will be selected from any available
provider that supports the transformation. If you request a transformation from
getInstance() that the provider does not support, a NoSuchAlgorithmException or
NoSuchPaddingException will be thrown. If you request a provider that is not installed, a
NoSuchProviderException is thrown.
The transformation string always includes the name of a cryptographic algorithm: for
example, DES. The standard names for common algorithms are listed in Table 10.3. Not all of
these algorithms are guaranteed to be available. In fact, JDK 1.2 doesn't supply any of these.
If you install JCE, you get access to Blowfish, DES, Triple DES, and PBEWithMD5AndDES.
You'll need a third-party provider to use RSA, IDEA, RC2, or RC4.
Table 10.3. JCE Standard Algorithm Names
Name Algorithm
The U.S. Federal government's Data Encryption Standard as defined by NIST in FIPS 46-1 and
DES 46-2; a symmetric 64-bit block cipher that uses a 56-bit key; see
DESede
http://www.itl.nist.gov/div897/pubs/fip46-2.htm.
DES e ncryption-d ecryption-e ncryption; triple DES; like DES, a 64-bit symmetric block cipher.
DES encryption with one 56-bit key is followed by decryption with a different 56-bit key, which
is followed by encryption with a third 56-bit key, effectively providing a 168-bit key space. It is
considered possible that the NSA cannot penetrate this algorithm.
PBEWithMD5 Password-Based Encryption as defined in RSA Laboratories, "PKCS #5: Password-Based
Encryption Standard," Version 1.5, Nov. 1993; based on DES; also requires a salt; see
AndDES http://www.rsa.com/rsalabs/pkcs/pkcs-5/index.html.
PBEWithMD5 Password-Based Encryption as defined in RSA Laboratories, "PKCS #5: Password-Based
Encryption Standard," version 1.5, Nov. 1993; based on DES; also requires a salt and an
AndTripleDES initialization vector; see http://www.rsa.com/rsalabs/pkcs/pkcs-5/index.html.
The patented Rivest, Shamir, and Adleman asymmetric cipher algorithm; RSA encryption as
RSA
defined in the RSA Laboratories Technical Note PKCS#1,
http://www.rsa.com/rsalabs/pkcs/pkcs-1/index.html. It is considered possible that the NSA
cannot penetrate this algorithm. [7] The patent expires in 2000.
7 I have a hunch (not necessarily shared by experts in the field) that RSA and similar algorithms will be broken someday by means much less
computationally intensive than brute force search. RSA's strength rests on the difficulty of factoring a large number into two large primes. However, it
is not known whether such factorization is fundamentally hard or whether we just don't yet know the right factoring algorithms. It seems obvious to
me that there's a lot of structure in the prime numbers that has yet to be exploited or understood by number theorists. For instance, the Goldbach
conjecture and the number of prime pairs are still unsolved questions. Therefore, I would not be surprised if far more efficient factorization algorithms
are discovered. Any such algorithm would severely reduce the strength of encryption schemes like RSA. Furthermore, there's been an explosion of
interest and research in quantum computing, following the discovery that RSA would be much more easily cracked by a quantum computer than by a
traditional one. This does not seem to be the case for public-key encryption schemes based on something other than prime factorization, for instance,
discrete logarithms or elliptic curves.
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