public final class SHA1 extends MessageDigest implements Cloneable
The FIPS PUB 180-2 standard specifies four secure hash algorithms (SHA-1, SHA-256, SHA-384 and SHA-512) for computing a condensed representation of electronic data (message). When a message of any length < 2^^64 bits (for SHA-1 and SHA-256) or < 2^^128 bits (for SHA-384 and SHA-512) is input to an algorithm, the result is an output called a message digest. The message digests range in length from 160 to 512 bits, depending on the algorithm. Secure hash algorithms are typically used with other cryptographic algorithms, such as digital signature algorithms and keyed-hash message authentication codes, or in the generation of random numbers (bits).
The four hash algorithms specified in this "SHS" standard are called secure because, for a given algorithm, it is computationally infeasible 1) to find a message that corresponds to a given message digest, or 2) to find two different messages that produce the same message digest. Any change to a message will, with a very high probability, result in a different message digest. This will result in a verification failure when the secure hash algorithm is used with a digital signature algorithm or a keyed-hash message authentication algorithm.
A "SHS change notice" adds a SHA-224 algorithm for interoperability, which, like SHA-1 and SHA-256, operates on 512-bit blocks and 32-bit words, but truncates the final digest and uses distinct initialization values.
References:
Modifier and Type | Field and Description |
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(package private) static int |
HASH_LENGTH
This implementation returns a fixed-size digest.
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Constructor and Description |
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SHA1()
Creates a SHA1 object with default initial state.
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Modifier and Type | Method and Description |
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Object |
clone()
Clones this object.
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byte[] |
engineDigest()
Completes the hash computation by performing final operations
such as padding.
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int |
engineDigest(byte[] hashvalue,
int offset,
int len)
Completes the hash computation by performing final operations
such as padding.
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int |
engineGetDigestLength()
Returns the digest length in bytes.
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protected void |
engineReset()
Reset athen initialize the digest context.
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void |
engineUpdate(byte input)
Updates the digest using the specified byte.
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void |
engineUpdate(byte[] input,
int offset,
int len)
Updates the digest using the specified array of bytes,
starting at the specified offset.
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static MessageDigest |
getInstance() |
protected void |
init()
Initialize the digest context.
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digest, digest, digest, getAlgorithm, getDigestLength, getInstance, getInstance, getInstance, getProvider, isEqual, reset, toString, update, update, update, update
engineUpdate
static final int HASH_LENGTH
public SHA1()
public static MessageDigest getInstance()
public Object clone() throws CloneNotSupportedException
clone
in class MessageDigest
CloneNotSupportedException
public int engineGetDigestLength()
java.security.MessageDigestSpi
.engineGetDigestLength
in class MessageDigestSpi
protected void engineReset()
java.security.MessageDigestSpi
.engineReset
in class MessageDigestSpi
protected void init()
public void engineUpdate(byte input)
engineUpdate
in class MessageDigestSpi
input
- the byte to use for the update.public void engineUpdate(byte[] input, int offset, int len)
engineUpdate
in class MessageDigestSpi
input
- the array of bytes to use for the update.offset
- the offset to start from in the array of bytes.len
- the number of bytes to use, starting at offset.public byte[] engineDigest()
engineDigest
in class MessageDigestSpi
public int engineDigest(byte[] hashvalue, int offset, int len) throws DigestException
engineDigest
in class MessageDigestSpi
hashvalue
- the output buffer in which to store the digest.offset
- offset to start from in the output bufferlen
- number of bytes within buf allotted for the digest.
Both this default implementation and the SUN provider
do not return partial digests. The presence of this
parameter is solely for consistency in our API's.
If the value of this parameter is less than the
actual digest length, the method will throw a
DigestException. This parameter is ignored if its
value is greater than or equal to the actual digest
length.DigestException