Cryptosystem - Revision history

Jnc: Make easier to read by breaking up some of my trademark run-on sentences

2026-10-16T08:37:52Z

Make easier to read by breaking up some of my trademark run-on sentences

← Older revision		Revision as of 08:37, 16 October 2026
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	A '''cryptosystem''' is a means by which one can transform 'clear' (i.e. original) data to 'encrypted' (i.e. hidden from view) data - i.e. it rearranges it in a way which is not easily reversible, by an arbitrary outsider. A cryptosystem consists of an [[algorithm]], used to effect the transformation (everyone using a particular cryptosystem has to know the algorithm; in fact, they are now usually widely publicized, although historically they were not) and a '''key''' (known only to the entities which are privy to a particular communication, one 'secured' with that cryptosystem and key).		A '''cryptosystem''' is a means by which one can transform 'clear' (i.e. original) data to 'encrypted' (i.e. hidden from view) data - i.e. it rearranges it in a way which is not easily reversible, by an arbitrary outsider. A cryptosystem consists of an [[algorithm]], used to effect the transformation (everyone using a particular cryptosystem has to know the algorithm; in fact, they are now usually widely publicized, although historically they were not), and a '''key''' (known only to the entities which are privy to a particular communication, one 'secured' with that cryptosystem and key).

	Starting with the 'clear text', the application of the algorithm, along with the key, produces 'encrypted text' (from the original clear text).		Starting with the 'clear text', the application of the algorithm, along with the key, produces 'encrypted text' (from the original clear text).

	A cryptosystem can be used to ''hide'' information from third parties (if one sends only the '''encrypted''' form of the information to someone else, a third party somehow obtaining a copy of the encrypted text cannot make any use of it)~~, or~~ ''secure'' (also called '''signing''') information (i.e. guarantee that a block of information is exactly that produced by the original sender).		A cryptosystem can be used to ''hide'' information from third parties (if one sends only the '''encrypted''' form of the information to someone else, a third party somehow obtaining a copy of the encrypted text cannot make any use of it). It can also be used to ''secure'' (also called '''signing''') information (i.e. guarantee that a block of information is exactly that produced by the original sender, and has not been tampered with by some third party).

	To do the latter, the originator produces a [[checksum]] of the original data block, and encrypts that with their chosen cryptosystem and key. ~~Even if~~ the original data block is then made widely, publicly, available, anyone who shares the key can verify that the copy they have received has not been tampered with~~, if they have a copy of the originator's computed checksum; they recompute~~ the checksum, re-encrypt it, and see if it matches ~~that~~ provided by the originator.		To do the latter, the originator produces a [[checksum]] of the original data block, and encrypts that with their chosen cryptosystem and key. If the original data block, along with the encrypted checksum, is then made widely, publicly, available, anyone who shares the key can verify that the copy of the block which they have received has not been tampered with. They re-compute the checksum, re-encrypt it, and see if it matches the encrypted checksum provided by the originator.

	{{semi-stub}}		{{semi-stub}}

Jnc: /* Further reading */ +The Alice and Bob After Dinner Speech - too hilarious not to link to _somewhere_

2026-10-13T11:25:26Z

Further reading: +The Alice and Bob After Dinner Speech - too hilarious not to link to _somewhere_

← Older revision		Revision as of 11:25, 13 October 2026
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	* Gordon Corera, ''Intercept: The Secret History of Computers and Spies'', Weidenfeld & Nicolson, London, 2015 - a good survey		* Gordon Corera, ''Intercept: The Secret History of Computers and Spies'', Weidenfeld & Nicolson, London, 2015 - a good survey
	* Jim DeBrosse, Colin Burke, ''The Secret in Building 26: The Untold Story of America's Ultra War Against the U-boat Enigma Codes'', Random House, New York, 2004 - industrial involvement in a large-scale attack on an early cryptosystem		* Jim DeBrosse, Colin Burke, ''The Secret in Building 26: The Untold Story of America's Ultra War Against the U-boat Enigma Codes'', Random House, New York, 2004 - industrial involvement in a large-scale attack on an early cryptosystem

			==External links==

			* [https://hex.ooo/library/alicebob.html The Alice and Bob After Dinner Speech] - too hilarious not to link to ''somewhere''

	[[Category: Security]]		[[Category: Security]]

Jnc: /* Further reading */ Add some

2026-10-04T09:52:19Z

Jnc: A decent first pass

2026-09-23T09:11:19Z

A decent first pass

New page

A '''cryptosystem''' is a means by which one can transform 'clear' (i.e. original) data to 'encrypted' (i.e. hidden from view) data - i.e. it rearranges it in a way which is not easily reversible, by an arbitrary outsider. A cryptosystem consists of an [[algorithm]], used to effect the transformation (everyone using a particular cryptosystem has to know the algorithm; in fact, they are now usually widely publicized, although historically they were not) and a '''key''' (known only to the entities which are privy to a particular communication, one 'secured' with that cryptosystem and key).

Starting with the 'clear text', the application of the algorithm, along with the key, produces 'encrypted text' (from the original clear text).

A cryptosystem can be used to ''hide'' information from third parties (if one sends only the '''encrypted''' form of the information to someone else, a third party somehow obtaining a copy of the encrypted text cannot make any use of it), or ''secure'' (also called '''signing''') information (i.e. guarantee that a block of information is exactly that produced by the original sender).

To do the latter, the originator produces a [[checksum]] of the original data block, and encrypts that with their chosen cryptosystem and key. Even if the original data block is then made widely, publicly, available, anyone who shares the key can verify that the copy they have received has not been tampered with, if they have a copy of the originator's computed checksum; they recompute the checksum, re-encrypt it, and see if it matches that provided by the originator.

{{semi-stub}}

==See also==

* [[Public key]]

[[Category: Security]]

← Older revision		Revision as of 09:52, 4 October 2026
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	* [[Public key]]		* [[Public key]]

			==Further reading==

			* David Kahn, ''The Codebreakers: The Story of Secret Writing'', Macmillan, New York, 1968 - the ground-breaking, voluminous history of the field
			* Gordon Corera, ''Intercept: The Secret History of Computers and Spies'', Weidenfeld & Nicolson, London, 2015 - a good survey
			* Jim DeBrosse, Colin Burke, ''The Secret in Building 26: The Untold Story of America's Ultra War Against the U-boat Enigma Codes'', Random House, New York, 2004 - industrial involvement in a large-scale attack on an early cryptosystem

	[[Category: Security]]		[[Category: Security]]