Does classifying an integer as a discrete log require it be part of a multiplicative group? Planned maintenance scheduled April 17/18, 2019 at 00:00UTC (8:00pm US/Eastern) Announcing the arrival of Valued Associate #679: Cesar Manara Unicorn Meta Zoo #1: Why another podcast?Discrete log problem, when we have many examplesFinding where I am in a linear recurrence relationA discrete-log-like problem, with matrices: given $A^k x$, find $k$iterated discrete log problemWhy can ECC key sizes be smaller than RSA keys for similar security?Is the reverse of the “discrete logarithm problem” equally dificult?How to construct a hash function into a cyclic group such that its discrete log is intractable?The computational complexity of discrete logSolving the discrete logarithm problem for a weak groupSolving discrete log in partially known group
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Does classifying an integer as a discrete log require it be part of a multiplicative group?
Planned maintenance scheduled April 17/18, 2019 at 00:00UTC (8:00pm US/Eastern)
Announcing the arrival of Valued Associate #679: Cesar Manara
Unicorn Meta Zoo #1: Why another podcast?Discrete log problem, when we have many examplesFinding where I am in a linear recurrence relationA discrete-log-like problem, with matrices: given $A^k x$, find $k$iterated discrete log problemWhy can ECC key sizes be smaller than RSA keys for similar security?Is the reverse of the “discrete logarithm problem” equally dificult?How to construct a hash function into a cyclic group such that its discrete log is intractable?The computational complexity of discrete logSolving the discrete logarithm problem for a weak groupSolving discrete log in partially known group
$begingroup$
This question is not a question about the discrete log problem, the generalized discrete log problem, or an additive group.
The confusion is whether any integer can be considered a discrete log or whether a discrete log has as a precondition, that it be part of a multiplicative group. This wikipedia would seem to indicate that the answer is yes.
For example 0 doesn't have a multiplicative inverse and is therefore not part of a multiplicative group.
discrete-logarithm terminology
asked 3 hours ago
JohnGaltJohnGalt
28528
$endgroup$
add a comment |
$begingroup$
This question is not a question about the discrete log problem, the generalized discrete log problem, or an additive group.
The confusion is whether any integer can be considered a discrete log or whether a discrete log has as a precondition, that it be part of a multiplicative group. This wikipedia would seem to indicate that the answer is yes.
For example 0 doesn't have a multiplicative inverse and is therefore not part of a multiplicative group.
discrete-logarithm terminology
asked 3 hours ago
JohnGaltJohnGalt
28528
$endgroup$
$begingroup$
@kelalaka Would you mind expanding upon "The discrete log is defined according to a base as the logarithm."
$endgroup$
– JohnGalt
2 hours ago
$begingroup$
@kelalaka also if "0 is not a part of the multiplicative group" does that mean that not all integers are part of a discrete log?
$endgroup$
– JohnGalt
2 hours ago
$begingroup$
Whomever down voted my question, I respect the decision, however, it would be helpful if you commented as to why you down voted it.
$endgroup$
– JohnGalt
1 hour ago
add a comment |
$begingroup$
This question is not a question about the discrete log problem, the generalized discrete log problem, or an additive group.
The confusion is whether any integer can be considered a discrete log or whether a discrete log has as a precondition, that it be part of a multiplicative group. This wikipedia would seem to indicate that the answer is yes.
For example 0 doesn't have a multiplicative inverse and is therefore not part of a multiplicative group.
discrete-logarithm terminology
asked 3 hours ago
JohnGaltJohnGalt
28528
$endgroup$
This question is not a question about the discrete log problem, the generalized discrete log problem, or an additive group.
The confusion is whether any integer can be considered a discrete log or whether a discrete log has as a precondition, that it be part of a multiplicative group. This wikipedia would seem to indicate that the answer is yes.
For example 0 doesn't have a multiplicative inverse and is therefore not part of a multiplicative group.
discrete-logarithm terminology
discrete-logarithm terminology
asked 3 hours ago
JohnGaltJohnGalt
28528
asked 3 hours ago
JohnGaltJohnGalt
28528
asked 3 hours ago
JohnGaltJohnGalt
28528
asked 3 hours ago
JohnGaltJohnGalt
28528
asked 3 hours ago
JohnGaltJohnGalt
28528
28528
$begingroup$
@kelalaka Would you mind expanding upon "The discrete log is defined according to a base as the logarithm."
$endgroup$
– JohnGalt
2 hours ago
$begingroup$
@kelalaka also if "0 is not a part of the multiplicative group" does that mean that not all integers are part of a discrete log?
$endgroup$
– JohnGalt
2 hours ago
$begingroup$
Whomever down voted my question, I respect the decision, however, it would be helpful if you commented as to why you down voted it.
$endgroup$
– JohnGalt
1 hour ago
add a comment |
$begingroup$
@kelalaka Would you mind expanding upon "The discrete log is defined according to a base as the logarithm."
$endgroup$
– JohnGalt
2 hours ago
$begingroup$
@kelalaka also if "0 is not a part of the multiplicative group" does that mean that not all integers are part of a discrete log?
$endgroup$
– JohnGalt
2 hours ago
$begingroup$
Whomever down voted my question, I respect the decision, however, it would be helpful if you commented as to why you down voted it.
$endgroup$
– JohnGalt
1 hour ago
$begingroup$
@kelalaka Would you mind expanding upon "The discrete log is defined according to a base as the logarithm."
$endgroup$
– JohnGalt
2 hours ago
$begingroup$
@kelalaka Would you mind expanding upon "The discrete log is defined according to a base as the logarithm."
$endgroup$
– JohnGalt
2 hours ago
$begingroup$
@kelalaka also if "0 is not a part of the multiplicative group" does that mean that not all integers are part of a discrete log?
$endgroup$
– JohnGalt
2 hours ago
$begingroup$
@kelalaka also if "0 is not a part of the multiplicative group" does that mean that not all integers are part of a discrete log?
$endgroup$
– JohnGalt
2 hours ago
$begingroup$
Whomever down voted my question, I respect the decision, however, it would be helpful if you commented as to why you down voted it.
$endgroup$
– JohnGalt
1 hour ago
$begingroup$
Whomever down voted my question, I respect the decision, however, it would be helpful if you commented as to why you down voted it.
$endgroup$
– JohnGalt
1 hour ago
add a comment |
2 Answers
2
active
oldest
votes
$begingroup$
The discrete logarithm $log_b a$ is an integer $x$ such that $b^x = a$. Similarly to the logarithms, we need a base, here $b$.
If the base is a generator of the group $g$ then any element of the group can be written as a power of the $g$ for some $k$, $y = g^k$. Therefore, the discrete log of $y$ according to base $g$ is $k$.
Take a generator $g$ of a multiplicative group $G$ with order $n$, and then take $g'=g^k$ where $gcd(k,n) neq 1$. Now the $g'$ will generate a subgroup $G'leqslant G$, not the full group. Then any element of the full group $ a in G$ and $a notin G'$ has not discrete logarithm according to base $g'$, even it is not a member of the subgroup.
When we consider the non-zero elements of a field $Fbackslash0$ they are forming a cyclic group under multiplication. For a proof see the Theorem 1.
answered 1 hour ago
kelalakakelalaka
8,85532351
$endgroup$
$begingroup$
It is very possible for $g^2$ to be a generator of $G$; in fact it will be one if and only if the order of $G$ is odd.
$endgroup$
– fkraiem
1 hour ago
$begingroup$
@fkraiem updated to guarantee that $g^k$ is generates a subgroup.
$endgroup$
– kelalaka
51 mins ago
add a comment |
$begingroup$
Of course any integer can be a discrete logarithm: in a group $G$ with generator $g$, any integer $x$ is a discrete logarithm of the group element $g^x$.
Another convenient way to consider the set of discrete logarithms is as the ring $mathbf Z/nmathbf Z$, where $n$ is the order of $G$, which makes sense because $g^x = g^x bmod n$ for all $x$. This is especially convenient when $n$ is prime because then the discrete logarithms form a field.
Either way (unless the group is trivial) the discrete logarithms form a non-trivial ring with unity, which is not a group for multiplication.
answered 1 hour ago
fkraiemfkraiem
6,79021732
$endgroup$
$begingroup$
what if n is a square? If n = k^2, then k is not a discrete log mod n.
$endgroup$
– grovkin
20 mins ago
$begingroup$
@grovkin Why not? $k$ is a discrete log of $g^k$. Are you confusing it with quadratic residue?
$endgroup$
– fkraiem
13 mins ago
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
The discrete logarithm $log_b a$ is an integer $x$ such that $b^x = a$. Similarly to the logarithms, we need a base, here $b$.
If the base is a generator of the group $g$ then any element of the group can be written as a power of the $g$ for some $k$, $y = g^k$. Therefore, the discrete log of $y$ according to base $g$ is $k$.
Take a generator $g$ of a multiplicative group $G$ with order $n$, and then take $g'=g^k$ where $gcd(k,n) neq 1$. Now the $g'$ will generate a subgroup $G'leqslant G$, not the full group. Then any element of the full group $ a in G$ and $a notin G'$ has not discrete logarithm according to base $g'$, even it is not a member of the subgroup.
When we consider the non-zero elements of a field $Fbackslash0$ they are forming a cyclic group under multiplication. For a proof see the Theorem 1.
answered 1 hour ago
kelalakakelalaka
8,85532351
$endgroup$
$begingroup$
It is very possible for $g^2$ to be a generator of $G$; in fact it will be one if and only if the order of $G$ is odd.
$endgroup$
– fkraiem
1 hour ago
$begingroup$
@fkraiem updated to guarantee that $g^k$ is generates a subgroup.
$endgroup$
– kelalaka
51 mins ago
add a comment |
$begingroup$
The discrete logarithm $log_b a$ is an integer $x$ such that $b^x = a$. Similarly to the logarithms, we need a base, here $b$.
If the base is a generator of the group $g$ then any element of the group can be written as a power of the $g$ for some $k$, $y = g^k$. Therefore, the discrete log of $y$ according to base $g$ is $k$.
Take a generator $g$ of a multiplicative group $G$ with order $n$, and then take $g'=g^k$ where $gcd(k,n) neq 1$. Now the $g'$ will generate a subgroup $G'leqslant G$, not the full group. Then any element of the full group $ a in G$ and $a notin G'$ has not discrete logarithm according to base $g'$, even it is not a member of the subgroup.
When we consider the non-zero elements of a field $Fbackslash0$ they are forming a cyclic group under multiplication. For a proof see the Theorem 1.
answered 1 hour ago
kelalakakelalaka
8,85532351
$endgroup$
$begingroup$
It is very possible for $g^2$ to be a generator of $G$; in fact it will be one if and only if the order of $G$ is odd.
$endgroup$
– fkraiem
1 hour ago
$begingroup$
@fkraiem updated to guarantee that $g^k$ is generates a subgroup.
$endgroup$
– kelalaka
51 mins ago
add a comment |
$begingroup$
The discrete logarithm $log_b a$ is an integer $x$ such that $b^x = a$. Similarly to the logarithms, we need a base, here $b$.
If the base is a generator of the group $g$ then any element of the group can be written as a power of the $g$ for some $k$, $y = g^k$. Therefore, the discrete log of $y$ according to base $g$ is $k$.
Take a generator $g$ of a multiplicative group $G$ with order $n$, and then take $g'=g^k$ where $gcd(k,n) neq 1$. Now the $g'$ will generate a subgroup $G'leqslant G$, not the full group. Then any element of the full group $ a in G$ and $a notin G'$ has not discrete logarithm according to base $g'$, even it is not a member of the subgroup.
When we consider the non-zero elements of a field $Fbackslash0$ they are forming a cyclic group under multiplication. For a proof see the Theorem 1.
answered 1 hour ago
kelalakakelalaka
8,85532351
$endgroup$
The discrete logarithm $log_b a$ is an integer $x$ such that $b^x = a$. Similarly to the logarithms, we need a base, here $b$.
If the base is a generator of the group $g$ then any element of the group can be written as a power of the $g$ for some $k$, $y = g^k$. Therefore, the discrete log of $y$ according to base $g$ is $k$.
Take a generator $g$ of a multiplicative group $G$ with order $n$, and then take $g'=g^k$ where $gcd(k,n) neq 1$. Now the $g'$ will generate a subgroup $G'leqslant G$, not the full group. Then any element of the full group $ a in G$ and $a notin G'$ has not discrete logarithm according to base $g'$, even it is not a member of the subgroup.
When we consider the non-zero elements of a field $Fbackslash0$ they are forming a cyclic group under multiplication. For a proof see the Theorem 1.
answered 1 hour ago
kelalakakelalaka
8,85532351
edited 52 mins ago
answered 1 hour ago
kelalakakelalaka
8,85532351
answered 1 hour ago
kelalakakelalaka
8,85532351
answered 1 hour ago
kelalakakelalaka
8,85532351
8,85532351
$begingroup$
It is very possible for $g^2$ to be a generator of $G$; in fact it will be one if and only if the order of $G$ is odd.
$endgroup$
– fkraiem
1 hour ago
$begingroup$
@fkraiem updated to guarantee that $g^k$ is generates a subgroup.
$endgroup$
– kelalaka
51 mins ago
add a comment |
$begingroup$
It is very possible for $g^2$ to be a generator of $G$; in fact it will be one if and only if the order of $G$ is odd.
$endgroup$
– fkraiem
1 hour ago
$begingroup$
@fkraiem updated to guarantee that $g^k$ is generates a subgroup.
$endgroup$
– kelalaka
51 mins ago
$begingroup$
It is very possible for $g^2$ to be a generator of $G$; in fact it will be one if and only if the order of $G$ is odd.
$endgroup$
– fkraiem
1 hour ago
$begingroup$
It is very possible for $g^2$ to be a generator of $G$; in fact it will be one if and only if the order of $G$ is odd.
$endgroup$
– fkraiem
1 hour ago
$begingroup$
@fkraiem updated to guarantee that $g^k$ is generates a subgroup.
$endgroup$
– kelalaka
51 mins ago
$begingroup$
@fkraiem updated to guarantee that $g^k$ is generates a subgroup.
$endgroup$
– kelalaka
51 mins ago
add a comment |
$begingroup$
Of course any integer can be a discrete logarithm: in a group $G$ with generator $g$, any integer $x$ is a discrete logarithm of the group element $g^x$.
Another convenient way to consider the set of discrete logarithms is as the ring $mathbf Z/nmathbf Z$, where $n$ is the order of $G$, which makes sense because $g^x = g^x bmod n$ for all $x$. This is especially convenient when $n$ is prime because then the discrete logarithms form a field.
Either way (unless the group is trivial) the discrete logarithms form a non-trivial ring with unity, which is not a group for multiplication.
answered 1 hour ago
fkraiemfkraiem
6,79021732
$endgroup$
$begingroup$
what if n is a square? If n = k^2, then k is not a discrete log mod n.
$endgroup$
– grovkin
20 mins ago
$begingroup$
@grovkin Why not? $k$ is a discrete log of $g^k$. Are you confusing it with quadratic residue?
$endgroup$
– fkraiem
13 mins ago
add a comment |
$begingroup$
Of course any integer can be a discrete logarithm: in a group $G$ with generator $g$, any integer $x$ is a discrete logarithm of the group element $g^x$.
Another convenient way to consider the set of discrete logarithms is as the ring $mathbf Z/nmathbf Z$, where $n$ is the order of $G$, which makes sense because $g^x = g^x bmod n$ for all $x$. This is especially convenient when $n$ is prime because then the discrete logarithms form a field.
Either way (unless the group is trivial) the discrete logarithms form a non-trivial ring with unity, which is not a group for multiplication.
answered 1 hour ago
fkraiemfkraiem
6,79021732
$endgroup$
$begingroup$
what if n is a square? If n = k^2, then k is not a discrete log mod n.
$endgroup$
– grovkin
20 mins ago
$begingroup$
@grovkin Why not? $k$ is a discrete log of $g^k$. Are you confusing it with quadratic residue?
$endgroup$
– fkraiem
13 mins ago
add a comment |
$begingroup$
Of course any integer can be a discrete logarithm: in a group $G$ with generator $g$, any integer $x$ is a discrete logarithm of the group element $g^x$.
Another convenient way to consider the set of discrete logarithms is as the ring $mathbf Z/nmathbf Z$, where $n$ is the order of $G$, which makes sense because $g^x = g^x bmod n$ for all $x$. This is especially convenient when $n$ is prime because then the discrete logarithms form a field.
Either way (unless the group is trivial) the discrete logarithms form a non-trivial ring with unity, which is not a group for multiplication.
answered 1 hour ago
fkraiemfkraiem
6,79021732
$endgroup$
Of course any integer can be a discrete logarithm: in a group $G$ with generator $g$, any integer $x$ is a discrete logarithm of the group element $g^x$.
Another convenient way to consider the set of discrete logarithms is as the ring $mathbf Z/nmathbf Z$, where $n$ is the order of $G$, which makes sense because $g^x = g^x bmod n$ for all $x$. This is especially convenient when $n$ is prime because then the discrete logarithms form a field.
Either way (unless the group is trivial) the discrete logarithms form a non-trivial ring with unity, which is not a group for multiplication.
answered 1 hour ago
fkraiemfkraiem
6,79021732
answered 1 hour ago
fkraiemfkraiem
6,79021732
answered 1 hour ago
fkraiemfkraiem
6,79021732
answered 1 hour ago
fkraiemfkraiem
6,79021732
6,79021732
$begingroup$
what if n is a square? If n = k^2, then k is not a discrete log mod n.
$endgroup$
– grovkin
20 mins ago
$begingroup$
@grovkin Why not? $k$ is a discrete log of $g^k$. Are you confusing it with quadratic residue?
$endgroup$
– fkraiem
13 mins ago
add a comment |
$begingroup$
what if n is a square? If n = k^2, then k is not a discrete log mod n.
$endgroup$
– grovkin
20 mins ago
$begingroup$
@grovkin Why not? $k$ is a discrete log of $g^k$. Are you confusing it with quadratic residue?
$endgroup$
– fkraiem
13 mins ago
$begingroup$
what if n is a square? If n = k^2, then k is not a discrete log mod n.
$endgroup$
– grovkin
20 mins ago
$begingroup$
what if n is a square? If n = k^2, then k is not a discrete log mod n.
$endgroup$
– grovkin
20 mins ago
$begingroup$
@grovkin Why not? $k$ is a discrete log of $g^k$. Are you confusing it with quadratic residue?
$endgroup$
– fkraiem
13 mins ago
$begingroup$
@grovkin Why not? $k$ is a discrete log of $g^k$. Are you confusing it with quadratic residue?
$endgroup$
– fkraiem
13 mins ago
add a comment |
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$begingroup$
@kelalaka Would you mind expanding upon "The discrete log is defined according to a base as the logarithm."
$endgroup$
– JohnGalt
2 hours ago
$begingroup$
@kelalaka also if "0 is not a part of the multiplicative group" does that mean that not all integers are part of a discrete log?
$endgroup$
– JohnGalt
2 hours ago
$begingroup$
Whomever down voted my question, I respect the decision, however, it would be helpful if you commented as to why you down voted it.
$endgroup$
– JohnGalt
1 hour ago