Class Hash

java.lang.Object

com.codename1.security.Hash

public final class Hash
extends Object

Streaming and one-shot cryptographic hash (message digest) functions. The supported algorithms are exposed as constants on this class:

• MD5 -- 128 bit, legacy interop only (broken collision resistance)
• SHA1 -- 160 bit, legacy interop only (broken collision resistance)
• SHA224 -- 224 bit (SHA-2 family)
• SHA256 -- 256 bit (SHA-2 family, recommended general-purpose hash)
• SHA384 -- 384 bit (SHA-2 family)
• SHA512 -- 512 bit (SHA-2 family)

Quick example

byte[] digest = Hash.sha256("hello".getBytes("UTF-8"));
String hex    = Hash.toHex(digest);

// streaming
Hash h = Hash.create(Hash.SHA256);
h.update("hello".getBytes("UTF-8"));
h.update(" world".getBytes("UTF-8"));
byte[] out = h.digest();

The implementations are written entirely in portable Java so they are available on every supported platform. They produce identical output to the equivalent algorithm in the standard JDK.

Field Summary

Fields

Modifier and Type	Field	Description
static final String	MD5	MD5 algorithm identifier (128-bit digest).
static final String	SHA1	SHA-1 algorithm identifier (160-bit digest).
static final String	SHA224	SHA-224 algorithm identifier (224-bit digest, SHA-2 family).
static final String	SHA256	SHA-256 algorithm identifier (256-bit digest, SHA-2 family).
static final String	SHA384	SHA-384 algorithm identifier (384-bit digest, SHA-2 family).
static final String	SHA512	SHA-512 algorithm identifier (512-bit digest, SHA-2 family).

Method Summary

Modifier and Type	Method	Description
static Hash	create(String algorithm)	Creates a streaming hash for the given algorithm.
byte[]	digest()	Finalises the running hash and returns the digest.
byte[]	digest(byte[] data)	Convenience: feed data then return the digest.
int	digestLength()	Number of bytes in the digest produced by this hash.
static byte[]	fromHex(String hex)	Decodes a hex string back into bytes.
static byte[]	md5(byte[] data)	One-shot MD5 hash.
void	reset()	Resets the running digest so the instance can be reused.
static byte[]	sha1(byte[] data)	One-shot SHA-1 hash.
static byte[]	sha224(byte[] data)	One-shot SHA-224 hash.
static byte[]	sha256(byte[] data)	One-shot SHA-256 hash (recommended general-purpose hash).
static byte[]	sha384(byte[] data)	One-shot SHA-384 hash.
static byte[]	sha512(byte[] data)	One-shot SHA-512 hash.
static String	toHex(byte[] data)	Encodes the bytes as a lowercase hex string (two characters per byte).
void	update(byte b)	Feeds a single byte into the running hash.
void	update(byte[] data)	Feeds the entire array into the running hash.
void	update(byte[] data, int offset, int length)	Feeds a slice of the array into the running hash.

Methods inherited from class Object

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

Field Details

MD5

public static final String MD5

MD5 algorithm identifier (128-bit digest). Provided for legacy interop -- MD5 is no longer considered collision resistant and should not be used for new security-sensitive code.

See Also:

• Constant Field Values

SHA1

public static final String SHA1

SHA-1 algorithm identifier (160-bit digest). Provided for legacy interop -- SHA-1 is no longer considered collision resistant and should not be used for new security-sensitive code.

See Also:

• Constant Field Values

SHA224

public static final String SHA224

SHA-224 algorithm identifier (224-bit digest, SHA-2 family).

See Also:

• Constant Field Values

SHA256

public static final String SHA256

SHA-256 algorithm identifier (256-bit digest, SHA-2 family). Recommended default for general-purpose hashing.

See Also:

• Constant Field Values

SHA384

public static final String SHA384

SHA-384 algorithm identifier (384-bit digest, SHA-2 family).

See Also:

• Constant Field Values

SHA512

public static final String SHA512

SHA-512 algorithm identifier (512-bit digest, SHA-2 family).

See Also:

• Constant Field Values

Method Details

create

public static Hash create(String algorithm)

Creates a streaming hash for the given algorithm.

Parameters

• algorithm: one of MD5, SHA1, SHA224, SHA256, SHA384, SHA512 -- case insensitive, with or without the dash

Returns

a new Hash instance with zero bytes consumed

Throws

• CryptoException: if the algorithm is not recognised

update

public void update(byte[] data)

Feeds the entire array into the running hash.

Parameters

• data: bytes to append to the running digest

update

public void update(byte[] data,
 int offset,
 int length)

Feeds a slice of the array into the running hash.

Parameters

• data: bytes to append to the running digest

• offset: index of the first byte to read

• length: number of bytes to read

update

public void update(byte b)

Feeds a single byte into the running hash.

digest

public byte[] digest()

Finalises the running hash and returns the digest. The hash is reset after this call so the same instance may be reused for another message.

Returns

the raw digest bytes (algorithm specific length)

digest

public byte[] digest(byte[] data)

Convenience: feed data then return the digest.

digestLength

public int digestLength()

Number of bytes in the digest produced by this hash.

reset

public void reset()

Resets the running digest so the instance can be reused.

md5

public static byte[] md5(byte[] data)

One-shot MD5 hash.

sha1

public static byte[] sha1(byte[] data)

One-shot SHA-1 hash.

sha224

public static byte[] sha224(byte[] data)

One-shot SHA-224 hash.

sha256

public static byte[] sha256(byte[] data)

One-shot SHA-256 hash (recommended general-purpose hash).

sha384

public static byte[] sha384(byte[] data)

One-shot SHA-384 hash.

sha512

public static byte[] sha512(byte[] data)

One-shot SHA-512 hash.

toHex

public static String toHex(byte[] data)

Encodes the bytes as a lowercase hex string (two characters per byte).

fromHex

public static byte[] fromHex(String hex)

Decodes a hex string back into bytes. The string must contain an even number of hex characters (whitespace and the 0x prefix are not stripped -- pass cleaned input).