Talk:Damm algorithm - Revision history

Protegmatic at 10:23, 17 August 2024

2024-08-17T10:23:09Z

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	{{oldafdfull\| date = 22 December 2012 (UTC) \| result = '''keep''' \| page = Damm algorithm }}{{WikiProject banner shell\|class=}}		{{oldafdfull\| date = 22 December 2012 (UTC) \| result = '''keep''' \| page = Damm algorithm }}{{WikiProject banner shell\|class=Start}}
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Johnhwoods: /* Trailing zeros? */

2024-04-20T11:31:35Z

Trailing zeros?

← Previous revision		Revision as of 11:31, 20 April 2024
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	== Trailing zeros? ==		== Trailing zeros? ==

	The article explains that leading ~~zeroes~~ have no effect on the checksum but that is probably not a weakness but a strength. If there is a weakness, surely it is that trailing zeros have no effect? 13, 130, 1300 and 13000 are all valid. An easy defence would be to reject all numbers ending in (one or more) ~~zeroes~~. [[User:Johnhwoods\|Johnhwoods]] ([[User talk:Johnhwoods\|talk]]) 08:44, 14 April 2024 (UTC)		The article explains that leading zeros have no effect on the checksum but that is probably not a weakness but a strength. If there is a weakness, surely it is that trailing zeros have no effect? 13, 130, 1300 and 13000 are all valid. An easy defence would be to reject all numbers ending in (one or more) zeros. [[User:Johnhwoods\|Johnhwoods]] ([[User talk:Johnhwoods\|talk]]) 08:44, 14 April 2024 (UTC)

			Whilst I'm thinking about zeros, the weaknesses section says that no checksum algorithm is affected by leading zeros. But it looks to me like Verhoeff is.

Johnhwoods: /* Trailing zeros? */ new section

2024-04-14T08:44:38Z

Trailing zeros?: new section

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	::: You are of course completely right -- I stupidly overlooked the initial 0 in the algorithm and examples, ouch. Thanks for taking the time to set me straight :). [[User:BlackFingolfin\|BlackFingolfin]] ([[User talk:BlackFingolfin\|talk]]) 08:26, 24 March 2015 (UTC)		::: You are of course completely right -- I stupidly overlooked the initial 0 in the algorithm and examples, ouch. Thanks for taking the time to set me straight :). [[User:BlackFingolfin\|BlackFingolfin]] ([[User talk:BlackFingolfin\|talk]]) 08:26, 24 March 2015 (UTC)

			== Trailing zeros? ==

			The article explains that leading zeroes have no effect on the checksum but that is probably not a weakness but a strength. If there is a weakness, surely it is that trailing zeros have no effect? 13, 130, 1300 and 13000 are all valid. An easy defence would be to reject all numbers ending in (one or more) zeroes. [[User:Johnhwoods\|Johnhwoods]] ([[User talk:Johnhwoods\|talk]]) 08:44, 14 April 2024 (UTC)

Qwerfjkl (bot): Adding {{WikiProject banner shell}} (Task 19)

2023-07-29T00:34:44Z

Adding {{WikiProject banner shell}} (Task 19)

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Cewbot: Reminder of an inactive anchor: powers

2023-01-09T02:18:12Z

Reminder of an inactive anchor: powers

← Previous revision		Revision as of 02:18, 9 January 2023
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	{{oldafdfull\| date = 22 December 2012 (UTC) \| result = '''keep''' \| page = Damm algorithm }}		{{oldafdfull\| date = 22 December 2012 (UTC) \| result = '''keep''' \| page = Damm algorithm }}
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			}}

	==Contested PROD==		==Contested PROD==

BlackFingolfin: /* In which cases does rearranging the rows not work? */

2015-03-24T08:26:42Z

In which cases does rearranging the rows not work?

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	:: After rearranging rows, the resulting quasigroup is ''weakly'' totally anti-symmetric. As you noticed 14 = 41, which violates the second requirement for TA-quasigroups. But notice that ''a''14 ≠ ''a''41 for all ''a'' ∈ ''Q'' and the algorithm described in the article uses a fixed prefix of ''a'' = 0 (interim digit initialized to 0), thus still detecting all adjacent transpositions. — [[User:MwGamera\|mwgamera]] ([[User talk:MwGamera\|talk]]) 16:18, 23 March 2015 (UTC)		:: After rearranging rows, the resulting quasigroup is ''weakly'' totally anti-symmetric. As you noticed 14 = 41, which violates the second requirement for TA-quasigroups. But notice that ''a''14 ≠ ''a''41 for all ''a'' ∈ ''Q'' and the algorithm described in the article uses a fixed prefix of ''a'' = 0 (interim digit initialized to 0), thus still detecting all adjacent transpositions. — [[User:MwGamera\|mwgamera]] ([[User talk:MwGamera\|talk]]) 16:18, 23 March 2015 (UTC)

			::: You are of course completely right -- I stupidly overlooked the initial 0 in the algorithm and examples, ouch. Thanks for taking the time to set me straight :). [[User:BlackFingolfin\|BlackFingolfin]] ([[User talk:BlackFingolfin\|talk]]) 08:26, 24 March 2015 (UTC)

MwGamera: /* In which cases does rearranging the rows not work? */

2015-03-23T16:18:41Z

In which cases does rearranging the rows not work?

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	: I am not quite sure what you mean with "rearranging the rows works" -- perhaps that the resulting quasigroup is still totally anti-symmetric? Well, I have not thought about your argument, but what I can say is that the table given on this Wikipedia page is not totally anti-symmetric, and hence the resulting checksum code does not detect all transposition errors. E.g. 41 and 14 both have checksum 1. While I am at it, I am confused as to why one would copy the quasigroup multiplication table from page 111 in Damm's thesis, which is inside a screenshot, instead of, say, taking the one on page 106... [[User:BlackFingolfin\|BlackFingolfin]] ([[User talk:BlackFingolfin\|talk]]) 08:49, 23 March 2015 (UTC)		: I am not quite sure what you mean with "rearranging the rows works" -- perhaps that the resulting quasigroup is still totally anti-symmetric? Well, I have not thought about your argument, but what I can say is that the table given on this Wikipedia page is not totally anti-symmetric, and hence the resulting checksum code does not detect all transposition errors. E.g. 41 and 14 both have checksum 1. While I am at it, I am confused as to why one would copy the quasigroup multiplication table from page 111 in Damm's thesis, which is inside a screenshot, instead of, say, taking the one on page 106... [[User:BlackFingolfin\|BlackFingolfin]] ([[User talk:BlackFingolfin\|talk]]) 08:49, 23 March 2015 (UTC)

			:: After rearranging rows, the resulting quasigroup is ''weakly'' totally anti-symmetric. As you noticed 14 = 41, which violates the second requirement for TA-quasigroups. But notice that ''a''14 ≠ ''a''41 for all ''a'' ∈ ''Q'' and the algorithm described in the article uses a fixed prefix of ''a'' = 0 (interim digit initialized to 0), thus still detecting all adjacent transpositions. — [[User:MwGamera\|mwgamera]] ([[User talk:MwGamera\|talk]]) 16:18, 23 March 2015 (UTC)

BlackFingolfin: /* In which cases does rearranging the rows not work? */

2015-03-23T08:49:43Z

In which cases does rearranging the rows not work?

← Previous revision		Revision as of 08:49, 23 March 2015
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	--[[User:W96\|W96]] ([[User talk:W96\|talk]]) 19:10, 18 January 2015 (UTC)		--[[User:W96\|W96]] ([[User talk:W96\|talk]]) 19:10, 18 January 2015 (UTC)

			: I am not quite sure what you mean with "rearranging the rows works" -- perhaps that the resulting quasigroup is still totally anti-symmetric? Well, I have not thought about your argument, but what I can say is that the table given on this Wikipedia page is not totally anti-symmetric, and hence the resulting checksum code does not detect all transposition errors. E.g. 41 and 14 both have checksum 1. While I am at it, I am confused as to why one would copy the quasigroup multiplication table from page 111 in Damm's thesis, which is inside a screenshot, instead of, say, taking the one on page 106... [[User:BlackFingolfin\|BlackFingolfin]] ([[User talk:BlackFingolfin\|talk]]) 08:49, 23 March 2015 (UTC)

W96: /* Algorithm? */ rm ellipsis

2015-02-11T19:42:58Z

Algorithm?: rm ellipsis

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	<blockquote>		<blockquote>
	Assuming a number … and a ~~"working~~ ~~digit"~~ w we then –		Assuming a number with digits numbered left to right <i>d<sub>1</sub>d<sub>2</sub>d<sub>3</sub>d<sub>4</sub></i> . . . and a “working digit” <i>w</i> we then –
	# Set w = 0		# Set <i>w</i> = 0
	# Successively set w = M[w, d<sub>i</sub>], working from the left (row w, column d<sub>i</sub> of the matrix).		# Successively set <i>w</i> = <i>M[w, d<sub>i</sub>]</i>, working from the left (row <i>w</i>, column <i>d<sub>i</sub></i> of the matrix).
	# Append the final w as the check digit.		# Append the final <i>w</i> as the check digit.
	</blockquote>		</blockquote>

MwGamera: /* Algorithm? */

2015-01-26T23:55:56Z

Algorithm?

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	:--[[User:W96\|W96]] ([[User talk:W96\|talk]]) 18:58, 18 January 2015 (UTC)		:--[[User:W96\|W96]] ([[User talk:W96\|talk]]) 18:58, 18 January 2015 (UTC)

			::Sorry for lack of earlier reply even though I especially bugged you about this. I can't check that reference, but I imagine it must have description of conditions that M[·,·] must satisfy and WTA-quasigroup operation satisfies them — in which case, that's what was needed here. Thanks for adding it. — [[User:MwGamera\|mwgamera]] ([[User talk:MwGamera\|talk]]) 23:51, 26 January 2015 (UTC)

	== In which cases does rearranging the rows not work? ==		== In which cases does rearranging the rows not work? ==

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	{{oldafdfull\| date = 22 December 2012 (UTC) \| result = '''keep''' \| page = Damm algorithm }}{{WikiProject banner shell\|class=}}		{{oldafdfull\| date = 22 December 2012 (UTC) \| result = '''keep''' \| page = Damm algorithm }}{{WikiProject banner shell\|class=Start}}
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