What is cryptography? | Journey into cryptography | Computer Science | Khan Academy
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0:08 - 0:09Imaginez que deux personnes qui partagent un important secret
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0:09 - 0:15doivent se séparer.
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0:15 - 0:17Cela les oblige à se transmettre
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0:17 - 0:20des informations privées à distance.
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0:20 - 0:21Par contre, une personne indiscrète nommée Eve
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0:21 - 0:23veut aussi cette information
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0:23 - 0:26et a la capacité d'intercepter leurs messages.
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0:26 - 0:28Alors, Alice décide de communiquer
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0:28 - 0:30en utilisant des lettres rédigées en code secret
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0:30 - 0:33L'analogie suivante va nous aider
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0:33 - 0:34D'abord, Alice enferme son message dans une boîte qu'elle verrouille,
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0:34 - 0:37avec un verrou dont seuls elle et bob
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0:37 - 0:39connaissent la combinaison.
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0:39 - 0:40C'est ce qu'on appelle un cryptage.
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0:40 - 0:43Ensuite, le message enfermé est envoyé à Bob
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0:46 - 0:48Et losque Bob reçoit la boite, il peut l'ouvrir
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0:48 - 0:51en utilisant le code partagé par avance
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0:51 - 0:55Ce processus est appelé décryptage
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0:55 - 0:58La cryptographie commence lorsque l'on abandonne le verrou physique
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0:58 - 1:00et que l'on utilise un chiffrement à la place
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1:00 - 1:03Voyez le chiffrement comme un verrou
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1:03 - 1:05Le chiffrement permet à Alice et Bob le brouillage
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1:05 - 1:07et le decryptage de leurs messages
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1:07 - 1:08ainsi ils parraissent n'avoir pas de sens
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1:08 - 1:11si Eve les intercepte.
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1:11 - 1:14La cryptographie existe depuis des milliers d'années.
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1:14 - 1:16Elle à été décisive en guerre et elle est le coeur
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1:16 - 1:19des réseaux de communication mondiaux aujourd'hui.
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1:19 - 1:21La fascinante histoire de la cryptographie
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1:21 - 1:24demande que l'on comprenne 2 vieilles idées
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1:24 - 1:28liée à la théorie des nombres et la théorie des probabilités.
- Title:
- What is cryptography? | Journey into cryptography | Computer Science | Khan Academy
- Description:
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Converting fractions to decimals sometimes requires us to brush up on our long division skills. We'll walk you through it.
Practice this lesson yourself on KhanAcademy.org right now: https://www.khanacademy.org/math/pre-algebra/decimals-pre-alg/decimal-to-fraction-pre-alg/e/converting_fractions_to_decimals?utm_source=YT&utm_medium=Desc&utm_campaign=PreAlgebra
Watch the next lesson: https://www.khanacademy.org/math/pre-algebra/decimals-pre-alg/decimal-to-fraction-pre-alg/v/decimals-and-fractions?utm_source=YT&utm_medium=Desc&utm_campaign=PreAlgebra
Missed the previous lesson?
https://www.khanacademy.org/math/pre-algebra/decimals-pre-alg/decimal-to-fraction-pre-alg/v/converting-fractions-to-decimals?utm_source=YT&utm_medium=Desc&utm_campaign=PreAlgebraPre-Algebra on Khan Academy: No way, this isn't your run of the mill arithmetic. This is Pre-algebra. You're about to play with the professionals. Think of pre-algebra as a runway. You're the airplane and algebra is your sunny vacation destination. Without the runway you're not going anywhere. Seriously, the foundation for all higher mathematics is laid with many of the concepts that we will introduce to you here: negative numbers, absolute value, factors, multiples, decimals, and fractions to name a few. So buckle up and move your seat into the upright position. We're about to take off!
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- English
- Team:
Khan Academy
- Duration:
- 01:31
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Fran Ontanaya edited French subtitles for What is cryptography? | Journey into cryptography | Computer Science | Khan Academy | |
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Fran Ontanaya edited French subtitles for What is cryptography? | Journey into cryptography | Computer Science | Khan Academy |