What does “constant rate” mean in universal composable commitment scheme?












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I'm wondering what does the "constant rate" mean in universal composable commitment scheme? I have known the rate of a commitment scheme is message length divided by the communication complexity of the scheme. What's the "constant" mean here? Must the constant be a number less than 1?










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  • $begingroup$
    Can you please post a reference to a paper or something where you encountered this term?
    $endgroup$
    – SEJPM
    Dec 18 '18 at 17:21
















3












$begingroup$


I'm wondering what does the "constant rate" mean in universal composable commitment scheme? I have known the rate of a commitment scheme is message length divided by the communication complexity of the scheme. What's the "constant" mean here? Must the constant be a number less than 1?










share|improve this question









$endgroup$












  • $begingroup$
    Can you please post a reference to a paper or something where you encountered this term?
    $endgroup$
    – SEJPM
    Dec 18 '18 at 17:21














3












3








3





$begingroup$


I'm wondering what does the "constant rate" mean in universal composable commitment scheme? I have known the rate of a commitment scheme is message length divided by the communication complexity of the scheme. What's the "constant" mean here? Must the constant be a number less than 1?










share|improve this question









$endgroup$




I'm wondering what does the "constant rate" mean in universal composable commitment scheme? I have known the rate of a commitment scheme is message length divided by the communication complexity of the scheme. What's the "constant" mean here? Must the constant be a number less than 1?







commitments






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asked Dec 18 '18 at 17:14









CryptoLoverCryptoLover

402212




402212












  • $begingroup$
    Can you please post a reference to a paper or something where you encountered this term?
    $endgroup$
    – SEJPM
    Dec 18 '18 at 17:21


















  • $begingroup$
    Can you please post a reference to a paper or something where you encountered this term?
    $endgroup$
    – SEJPM
    Dec 18 '18 at 17:21
















$begingroup$
Can you please post a reference to a paper or something where you encountered this term?
$endgroup$
– SEJPM
Dec 18 '18 at 17:21




$begingroup$
Can you please post a reference to a paper or something where you encountered this term?
$endgroup$
– SEJPM
Dec 18 '18 at 17:21










1 Answer
1






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4












$begingroup$

Constant rate in general means that the overhead from a non-secure method is constant. So, in a simple way, if I am committing to an $ell$-bit message, then the size of the commitment is $O(ell)$. In some cases, however, one also allows an additive factor that is independent of the message size. Thus, for example, it could be that to commit to a message of size $ell$ the amount is $O(ell)+{rm poly}(n)$, where $n$ is the security parameter.



Note that typically these are measured in an amortized manner. So, you have to send many commitments (or a long message) for it to be true. But, again, this depends on the exact scheme, so you'll have to read the details.






share|improve this answer









$endgroup$













  • $begingroup$
    Thanks for your answer. I have one more question: how large the size of the commitment is would be regarded as bad? For example, if the size of the commitment is O(nl) for committing l-bit message, where n is security parameter, is it bad?
    $endgroup$
    – CryptoLover
    Jan 10 at 16:50










  • $begingroup$
    Good or bad depends on your setting and what you want. In general, $O(ncdotell)$ is of course much worse than $O(ell)+poly(n)$, but if you want to commit to a little bit only, sometimes a simpler scheme is better.
    $endgroup$
    – Yehuda Lindell
    Jan 11 at 1:23











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1 Answer
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1 Answer
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active

oldest

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4












$begingroup$

Constant rate in general means that the overhead from a non-secure method is constant. So, in a simple way, if I am committing to an $ell$-bit message, then the size of the commitment is $O(ell)$. In some cases, however, one also allows an additive factor that is independent of the message size. Thus, for example, it could be that to commit to a message of size $ell$ the amount is $O(ell)+{rm poly}(n)$, where $n$ is the security parameter.



Note that typically these are measured in an amortized manner. So, you have to send many commitments (or a long message) for it to be true. But, again, this depends on the exact scheme, so you'll have to read the details.






share|improve this answer









$endgroup$













  • $begingroup$
    Thanks for your answer. I have one more question: how large the size of the commitment is would be regarded as bad? For example, if the size of the commitment is O(nl) for committing l-bit message, where n is security parameter, is it bad?
    $endgroup$
    – CryptoLover
    Jan 10 at 16:50










  • $begingroup$
    Good or bad depends on your setting and what you want. In general, $O(ncdotell)$ is of course much worse than $O(ell)+poly(n)$, but if you want to commit to a little bit only, sometimes a simpler scheme is better.
    $endgroup$
    – Yehuda Lindell
    Jan 11 at 1:23
















4












$begingroup$

Constant rate in general means that the overhead from a non-secure method is constant. So, in a simple way, if I am committing to an $ell$-bit message, then the size of the commitment is $O(ell)$. In some cases, however, one also allows an additive factor that is independent of the message size. Thus, for example, it could be that to commit to a message of size $ell$ the amount is $O(ell)+{rm poly}(n)$, where $n$ is the security parameter.



Note that typically these are measured in an amortized manner. So, you have to send many commitments (or a long message) for it to be true. But, again, this depends on the exact scheme, so you'll have to read the details.






share|improve this answer









$endgroup$













  • $begingroup$
    Thanks for your answer. I have one more question: how large the size of the commitment is would be regarded as bad? For example, if the size of the commitment is O(nl) for committing l-bit message, where n is security parameter, is it bad?
    $endgroup$
    – CryptoLover
    Jan 10 at 16:50










  • $begingroup$
    Good or bad depends on your setting and what you want. In general, $O(ncdotell)$ is of course much worse than $O(ell)+poly(n)$, but if you want to commit to a little bit only, sometimes a simpler scheme is better.
    $endgroup$
    – Yehuda Lindell
    Jan 11 at 1:23














4












4








4





$begingroup$

Constant rate in general means that the overhead from a non-secure method is constant. So, in a simple way, if I am committing to an $ell$-bit message, then the size of the commitment is $O(ell)$. In some cases, however, one also allows an additive factor that is independent of the message size. Thus, for example, it could be that to commit to a message of size $ell$ the amount is $O(ell)+{rm poly}(n)$, where $n$ is the security parameter.



Note that typically these are measured in an amortized manner. So, you have to send many commitments (or a long message) for it to be true. But, again, this depends on the exact scheme, so you'll have to read the details.






share|improve this answer









$endgroup$



Constant rate in general means that the overhead from a non-secure method is constant. So, in a simple way, if I am committing to an $ell$-bit message, then the size of the commitment is $O(ell)$. In some cases, however, one also allows an additive factor that is independent of the message size. Thus, for example, it could be that to commit to a message of size $ell$ the amount is $O(ell)+{rm poly}(n)$, where $n$ is the security parameter.



Note that typically these are measured in an amortized manner. So, you have to send many commitments (or a long message) for it to be true. But, again, this depends on the exact scheme, so you'll have to read the details.







share|improve this answer












share|improve this answer



share|improve this answer










answered Dec 18 '18 at 17:34









Yehuda LindellYehuda Lindell

18.6k3661




18.6k3661












  • $begingroup$
    Thanks for your answer. I have one more question: how large the size of the commitment is would be regarded as bad? For example, if the size of the commitment is O(nl) for committing l-bit message, where n is security parameter, is it bad?
    $endgroup$
    – CryptoLover
    Jan 10 at 16:50










  • $begingroup$
    Good or bad depends on your setting and what you want. In general, $O(ncdotell)$ is of course much worse than $O(ell)+poly(n)$, but if you want to commit to a little bit only, sometimes a simpler scheme is better.
    $endgroup$
    – Yehuda Lindell
    Jan 11 at 1:23


















  • $begingroup$
    Thanks for your answer. I have one more question: how large the size of the commitment is would be regarded as bad? For example, if the size of the commitment is O(nl) for committing l-bit message, where n is security parameter, is it bad?
    $endgroup$
    – CryptoLover
    Jan 10 at 16:50










  • $begingroup$
    Good or bad depends on your setting and what you want. In general, $O(ncdotell)$ is of course much worse than $O(ell)+poly(n)$, but if you want to commit to a little bit only, sometimes a simpler scheme is better.
    $endgroup$
    – Yehuda Lindell
    Jan 11 at 1:23
















$begingroup$
Thanks for your answer. I have one more question: how large the size of the commitment is would be regarded as bad? For example, if the size of the commitment is O(nl) for committing l-bit message, where n is security parameter, is it bad?
$endgroup$
– CryptoLover
Jan 10 at 16:50




$begingroup$
Thanks for your answer. I have one more question: how large the size of the commitment is would be regarded as bad? For example, if the size of the commitment is O(nl) for committing l-bit message, where n is security parameter, is it bad?
$endgroup$
– CryptoLover
Jan 10 at 16:50












$begingroup$
Good or bad depends on your setting and what you want. In general, $O(ncdotell)$ is of course much worse than $O(ell)+poly(n)$, but if you want to commit to a little bit only, sometimes a simpler scheme is better.
$endgroup$
– Yehuda Lindell
Jan 11 at 1:23




$begingroup$
Good or bad depends on your setting and what you want. In general, $O(ncdotell)$ is of course much worse than $O(ell)+poly(n)$, but if you want to commit to a little bit only, sometimes a simpler scheme is better.
$endgroup$
– Yehuda Lindell
Jan 11 at 1:23


















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