Mixing
Generate hash from chunked file
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I'm programming a web service for uploading long files. The client sends the chunks whenever it wants. I need to calculate the hash of this file while theese chunks are received.
I've seen that you can do somenthing like this:
byte buf = new byte[8192];
MessageDigest sha = MessageDigest.getInstance("SHA1");
FileInputStream inp = new FileInputStream(new File("D:\season4_mlp.rar"));
int n;
while((n = inp.read(buf)) > 0)
sha.update(buf, 0, n);
byte hash = sha.digest();
The problem is that I need to do this with different chunks of the same file and I don't know when they are going to come. I would need to keep the state of this hash calculation.
java hash cryptography bouncycastle message-digest
asked yesterday
Enrique de Miguel
11819
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up vote
0
down vote
favorite
I'm programming a web service for uploading long files. The client sends the chunks whenever it wants. I need to calculate the hash of this file while theese chunks are received.
I've seen that you can do somenthing like this:
byte buf = new byte[8192];
MessageDigest sha = MessageDigest.getInstance("SHA1");
FileInputStream inp = new FileInputStream(new File("D:\season4_mlp.rar"));
int n;
while((n = inp.read(buf)) > 0)
sha.update(buf, 0, n);
byte hash = sha.digest();
The problem is that I need to do this with different chunks of the same file and I don't know when they are going to come. I would need to keep the state of this hash calculation.
java hash cryptography bouncycastle message-digest
asked yesterday
Enrique de Miguel
11819
The code you posted doesn't require BouncyCastle, and unless you've jiggered your provider list doesn't use it at all. But if you mean you want to hash the data chunks out of order, you can't do that, not with JCE nor with BC LWAPI, because that's altering the data which is exactly what any decent crypto-hash and even SHA1 is designed to prevent.
– dave_thompson_085
yesterday
I will work the hash out using the chunks in order. The question it's been edited for better undestanding... In the example I haveMessageDigest shathat it's used to generate the final hash. The point is that there is a gap between one chunk and the next one and so I have to keep the state ofMessageDigest shauntil I have all the data and then I can dobyte hash = sha.digest();
– Enrique de Miguel
yesterday
1
The MessageDigest objects retains all the necessary state. That's why there's anupdate()method.
– James K Polk
yesterday
add a comment |
up vote
0
down vote
favorite
up vote
0
down vote
favorite
I'm programming a web service for uploading long files. The client sends the chunks whenever it wants. I need to calculate the hash of this file while theese chunks are received.
I've seen that you can do somenthing like this:
byte buf = new byte[8192];
MessageDigest sha = MessageDigest.getInstance("SHA1");
FileInputStream inp = new FileInputStream(new File("D:\season4_mlp.rar"));
int n;
while((n = inp.read(buf)) > 0)
sha.update(buf, 0, n);
byte hash = sha.digest();
The problem is that I need to do this with different chunks of the same file and I don't know when they are going to come. I would need to keep the state of this hash calculation.
java hash cryptography bouncycastle message-digest
asked yesterday
Enrique de Miguel
11819
I'm programming a web service for uploading long files. The client sends the chunks whenever it wants. I need to calculate the hash of this file while theese chunks are received.
I've seen that you can do somenthing like this:
byte buf = new byte[8192];
MessageDigest sha = MessageDigest.getInstance("SHA1");
FileInputStream inp = new FileInputStream(new File("D:\season4_mlp.rar"));
int n;
while((n = inp.read(buf)) > 0)
sha.update(buf, 0, n);
byte hash = sha.digest();
The problem is that I need to do this with different chunks of the same file and I don't know when they are going to come. I would need to keep the state of this hash calculation.
java hash cryptography bouncycastle message-digest
java hash cryptography bouncycastle message-digest
asked yesterday
Enrique de Miguel
11819
asked yesterday
Enrique de Miguel
11819
edited yesterday
asked yesterday
Enrique de Miguel
11819
asked yesterday
Enrique de Miguel
11819
asked yesterday
Enrique de Miguel
11819
11819
The code you posted doesn't require BouncyCastle, and unless you've jiggered your provider list doesn't use it at all. But if you mean you want to hash the data chunks out of order, you can't do that, not with JCE nor with BC LWAPI, because that's altering the data which is exactly what any decent crypto-hash and even SHA1 is designed to prevent.
– dave_thompson_085
yesterday
I will work the hash out using the chunks in order. The question it's been edited for better undestanding... In the example I haveMessageDigest shathat it's used to generate the final hash. The point is that there is a gap between one chunk and the next one and so I have to keep the state ofMessageDigest shauntil I have all the data and then I can dobyte hash = sha.digest();
– Enrique de Miguel
yesterday
1
The MessageDigest objects retains all the necessary state. That's why there's anupdate()method.
– James K Polk
yesterday
add a comment |
The code you posted doesn't require BouncyCastle, and unless you've jiggered your provider list doesn't use it at all. But if you mean you want to hash the data chunks out of order, you can't do that, not with JCE nor with BC LWAPI, because that's altering the data which is exactly what any decent crypto-hash and even SHA1 is designed to prevent.
– dave_thompson_085
yesterday
I will work the hash out using the chunks in order. The question it's been edited for better undestanding... In the example I haveMessageDigest shathat it's used to generate the final hash. The point is that there is a gap between one chunk and the next one and so I have to keep the state ofMessageDigest shauntil I have all the data and then I can dobyte hash = sha.digest();
– Enrique de Miguel
yesterday
1
The MessageDigest objects retains all the necessary state. That's why there's anupdate()method.
– James K Polk
yesterday
The code you posted doesn't require BouncyCastle, and unless you've jiggered your provider list doesn't use it at all. But if you mean you want to hash the data chunks out of order, you can't do that, not with JCE nor with BC LWAPI, because that's altering the data which is exactly what any decent crypto-hash and even SHA1 is designed to prevent.
– dave_thompson_085
yesterday
The code you posted doesn't require BouncyCastle, and unless you've jiggered your provider list doesn't use it at all. But if you mean you want to hash the data chunks out of order, you can't do that, not with JCE nor with BC LWAPI, because that's altering the data which is exactly what any decent crypto-hash and even SHA1 is designed to prevent.
– dave_thompson_085
yesterday
I will work the hash out using the chunks in order. The question it's been edited for better undestanding... In the example I have
MessageDigest sha that it's used to generate the final hash. The point is that there is a gap between one chunk and the next one and so I have to keep the state of MessageDigest sha until I have all the data and then I can do byte hash = sha.digest();– Enrique de Miguel
yesterday
I will work the hash out using the chunks in order. The question it's been edited for better undestanding... In the example I have
MessageDigest sha that it's used to generate the final hash. The point is that there is a gap between one chunk and the next one and so I have to keep the state of MessageDigest sha until I have all the data and then I can do byte hash = sha.digest();– Enrique de Miguel
yesterday
1
1
The MessageDigest objects retains all the necessary state. That's why there's an
update() method.– James K Polk
yesterday
The MessageDigest objects retains all the necessary state. That's why there's an
update() method.– James K Polk
yesterday
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The code you posted doesn't require BouncyCastle, and unless you've jiggered your provider list doesn't use it at all. But if you mean you want to hash the data chunks out of order, you can't do that, not with JCE nor with BC LWAPI, because that's altering the data which is exactly what any decent crypto-hash and even SHA1 is designed to prevent.
– dave_thompson_085
yesterday
I will work the hash out using the chunks in order. The question it's been edited for better undestanding... In the example I have
MessageDigest shathat it's used to generate the final hash. The point is that there is a gap between one chunk and the next one and so I have to keep the state ofMessageDigest shauntil I have all the data and then I can dobyte hash = sha.digest();– Enrique de Miguel
yesterday
1
The MessageDigest objects retains all the necessary state. That's why there's an
update()method.– James K Polk
yesterday