Signing short messages

[roy7]

I don't know much about encryption but I recall some older forms had security issues if you had messages that were too short. (Shorter than the key length? Not sure.) Is there any similar issues with signing messages with bitcoin? If I ask someone to sign a single word for instance, just 4-10 characters long, is that any sort of a security issue?

Thanks.

[kodo]

I don't know much about encryption but I recall some older forms had security issues if you had messages that were too short. (Shorter than the key length? Not sure.) Is there any similar issues with signing messages with bitcoin? If I ask someone to sign a single word for instance, just 4-10 characters long, is that any sort of a security issue?

Thanks.

I still dont understand how to encrypt text..

[roy7]

I don't know much about encryption but I recall some older forms had security issues if you had messages that were too short. (Shorter than the key length? Not sure.) Is there any similar issues with signing messages with bitcoin? If I ask someone to sign a single word for instance, just 4-10 characters long, is that any sort of a security issue?

Thanks.

I still dont understand how to encrypt text..

Bitcoin doesn't do any encryption of text, but it can sign text to prove you own the public key. Since it's the same underlying science as normal public key encryption I wanted to be sure signing short messages didn't open any sort of attack on the private key.

[domob]

Don't take my word for it (I'm neither expert with the code nor with crypto), but I presume for signing a message you first hash it and then sign the hash.  Thus it is completely irrelevant how large the message is because you always end up doing your crypto on a fixed-size hash.

[kjj]

Don't take my word for it (I'm neither expert with the code nor with crypto), but I presume for signing a message you first hash it and then sign the hash.  Thus it is completely irrelevant how large the message is because you always end up doing your crypto on a fixed-size hash.

Code:

    vector<unsigned char> vchSig;
    if (!key.SignCompact(Hash(ss.begin(), ss.end()), vchSig))
        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Sign failed");

Yup.

[roy7]

Ok cool, thank you!

[jackjack]

I don't know much about encryption but I recall some older forms had security issues if you had messages that were too short. (Shorter than the key length? Not sure.) Is there any similar issues with signing messages with bitcoin? If I ask someone to sign a single word for instance, just 4-10 characters long, is that any sort of a security issue?

Thanks.

I still dont understand how to encrypt text..

Bitcoin doesn't do any encryption of text, but it can sign text to prove you own the public key. Since it's the same underlying science as normal public key encryption I wanted to be sure signing short messages didn't open any sort of attack on the private key.

You can encrypt text with bitcoin private keys

[threeip]

I don't know much about encryption but I recall some older forms had security issues if you had messages that were too short. (Shorter than the key length? Not sure.) Is there any similar issues with signing messages with bitcoin? If I ask someone to sign a single word for instance, just 4-10 characters long, is that any sort of a security issue?

Thanks.

I still dont understand how to encrypt text..

Bitcoin doesn't do any encryption of text, but it can sign text to prove you own the public key. Since it's the same underlying science as normal public key encryption I wanted to be sure signing short messages didn't open any sort of attack on the private key.

You can encrypt text with bitcoin private keys

But you cant encrypt with public key and decrypt with private key, right..?

[jackjack]

I don't know much about encryption but I recall some older forms had security issues if you had messages that were too short. (Shorter than the key length? Not sure.) Is there any similar issues with signing messages with bitcoin? If I ask someone to sign a single word for instance, just 4-10 characters long, is that any sort of a security issue?

Thanks.

I still dont understand how to encrypt text..

Bitcoin doesn't do any encryption of text, but it can sign text to prove you own the public key. Since it's the same underlying science as normal public key encryption I wanted to be sure signing short messages didn't open any sort of attack on the private key.

You can encrypt text with bitcoin private keys

But you cant encrypt with public key and decrypt with private key, right..?

No, you can (that's what I meant, sorry for being unclear)
For now, the clients themselves don't do that but it is possible as I made an implementation

[Boussac]

I don't know much about encryption but I recall some older forms had security issues if you had messages that were too short. (Shorter than the key length? Not sure.) Is there any similar issues with signing messages with bitcoin? If I ask someone to sign a single word for instance, just 4-10 characters long, is that any sort of a security issue?

Thanks.

I still dont understand how to encrypt text..

Bitcoin doesn't do any encryption of text, but it can sign text to prove you own the public key. Since it's the same underlying science as normal public key encryption I wanted to be sure signing short messages didn't open any sort of attack on the private key.

You can encrypt text with bitcoin private keys

But you cant encrypt with public key and decrypt with private key, right..?

No, you can (that's what I meant, sorry for being unclear)
For now, the clients themselves don't do that but it is possible as I made an implementation

Are you referring to an implementation of ECIES encryption ?

[jackjack]

I don't know much about encryption but I recall some older forms had security issues if you had messages that were too short. (Shorter than the key length? Not sure.) Is there any similar issues with signing messages with bitcoin? If I ask someone to sign a single word for instance, just 4-10 characters long, is that any sort of a security issue?

Thanks.

I still dont understand how to encrypt text..

Bitcoin doesn't do any encryption of text, but it can sign text to prove you own the public key. Since it's the same underlying science as normal public key encryption I wanted to be sure signing short messages didn't open any sort of attack on the private key.

You can encrypt text with bitcoin private keys

But you cant encrypt with public key and decrypt with private key, right..?

No, you can (that's what I meant, sorry for being unclear)
For now, the clients themselves don't do that but it is possible as I made an implementation

Are you referring to an implementation of ECIES encryption ?

No, somebody pointed me to ECIES when I released my software but I never had the time to look at it. I'm not even sure anyone used it with Bitcoin BTW
I'm using secret sharing