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Jeudi 27 septembre - Pour la première fois au Québec, la chasse et le piégeage sont interdits en raison de la maladie débilitante chronique (MDC) chez les cervidés.

Des outils qui permettent de manipuler le téléphone ou la tablette, de la simuler par une machine virtuelle , de créer des fichiers APK les fichiers de paquet d'Android , de déboguer les applications et d'y ajouter une signature numérique. Une sculpture d'un bugdroid , accompagnée par une sculpture de chaque pâtisserie utilisée comme nom de code des différentes versions d'Android est placée devant le centre de développement Google. The numbers p and q should not be "too close", lest the Fermat factorization for n be successful. A quoi ça sert de savoir résoudre un problème? Friendica est également libre et décentralisé et propose beaucoup de fonctionnalités qui peuvent manquer dans les autres alternatives:.

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RSA (Rivest–Shamir–Adleman) is one of the first public-key cryptosystems and is widely used for secure data transmission. In such a cryptosystem, the encryption key is public and it is different from the decryption key which is kept secret (private). In RSA, this asymmetry is based on the practical difficulty of the factorization of the product of two .

Patent 4,, for a "Cryptographic communications system and method" that used the algorithm, on September 20, Though the patent was going to expire on September 21, the term of patent was 17 years at the time , the algorithm was released to the public domain by RSA Security on September 6, , two weeks earlier. Had Cocks's work been publicly known, a patent in the United States would not have been legal either. From the DWPI 's abstract of the patent,.

The system includes a communications channel coupled to at least one terminal having an encoding device and to at least one terminal having a decoding device. A message-to-be-transferred is enciphered to ciphertext at the encoding terminal by encoding the message as a number M in a predetermined set. That number is then raised to a first predetermined power associated with the intended receiver and finally computed.

The remainder or residue, C, is The RSA algorithm involves four steps: In addition, for some operations it is convenient that the order of the two exponentiations can be changed and that this relation also implies:.

RSA involves a public key and a private key. The public key can be known by everyone, and it is used for encrypting messages. The intention is that messages encrypted with the public key can only be decrypted in a reasonable amount of time by using the private key.

The public key is represented by the integers n and e ; and, the private key, by the integer d although n is also used during the decryption process. Thus, it might be considered to be a part of the private key, too. The public key consists of the modulus n and the public or encryption exponent e. The private key consists of the private or decryption exponent d , which must be kept secret.

That the Euler totient function can be used can also be seen as a consequence of the Lagrange's theorem applied to the multiplicative group of integers modulo pq. Since it is beneficial to use a small value for e e. Suppose that Bob wants to send information to Alice. If they decide to use RSA, Bob must know Alice's public key to encrypt the message and Alice must use her private key to decrypt the message. To enable Bob to send his encrypted messages, Alice transmits her public key n , e to Bob via a reliable, but not necessarily secret, route.

Alice's private key d is never distributed. After Bob obtains Alice's public key, he can send a message M to Alice. He then computes the ciphertext c , using Alice's public key e , corresponding to. This can be done reasonably quickly, even for bit numbers, using modular exponentiation. Bob then transmits c to Alice. Alice can recover m from c by using her private key exponent d by computing. Given m , she can recover the original message M by reversing the padding scheme.

Here is an example of RSA encryption and decryption. The parameters used here are artificially small, but one can also use OpenSSL to generate and examine a real keypair.

For a padded plaintext message m , the encryption function is. For an encrypted ciphertext c , the decryption function is. Both of these calculations can be computed efficiently using the square-and-multiply algorithm for modular exponentiation.

In real-life situations the primes selected would be much larger; in our example it would be trivial to factor n , obtained from the freely available public key back to the primes p and q. Practical implementations use the Chinese remainder theorem to speed up the calculation using modulus of factors mod pq using mod p and mod q. The values d p , d q and q inv , which are part of the private key are computed as follows:. Here is how d p , d q and q inv are used for efficient decryption.

Encryption is efficient by choice of a suitable d and e pair. A working example in JavaScript using BigInteger. This code should not be used in production, as bigInt. Suppose Alice uses Bob 's public key to send him an encrypted message. In the message, she can claim to be Alice but Bob has no way of verifying that the message was actually from Alice since anyone can use Bob's public key to send him encrypted messages.

In order to verify the origin of a message, RSA can also be used to sign a message. Suppose Alice wishes to send a signed message to Bob. She can use her own private key to do so. She produces a hash value of the message, raises it to the power of d modulo n as she does when decrypting a message , and attaches it as a "signature" to the message.

When Bob receives the signed message, he uses the same hash algorithm in conjunction with Alice's public key. He raises the signature to the power of e modulo n as he does when encrypting a message , and compares the resulting hash value with the message's actual hash value. If the two agree, he knows that the author of the message was in possession of Alice's private key, and that the message has not been tampered with since. Although the original paper of Rivest, Shamir, and Adleman used Fermat's little theorem to explain why RSA works, it is common to find proofs that rely instead on Euler's theorem.

Assuming that m is relatively prime to n , we have. When m is not relatively prime to n , the argument just given is invalid. To avoid these problems, practical RSA implementations typically embed some form of structured, randomized padding into the value m before encrypting it.

This padding ensures that m does not fall into the range of insecure plaintexts, and that a given message, once padded, will encrypt to one of a large number of different possible ciphertexts. Because these schemes pad the plaintext m with some number of additional bits, the size of the un-padded message M must be somewhat smaller. RSA padding schemes must be carefully designed so as to prevent sophisticated attacks which may be facilitated by a predictable message structure.

Early versions of the PKCS 1 standard up to version 1. However, at Crypto , Bleichenbacher showed that this version is vulnerable to a practical adaptive chosen ciphertext attack.

Furthermore, at Eurocrypt , Coron et al. Secure padding schemes such as RSA-PSS are as essential for the security of message signing as they are for message encryption. Use of PSS no longer seems to be encumbered by patents.

Note that using different RSA key-pairs for encryption and signing is potentially more secure. NET use the following optimization for decryption and signing based on the Chinese remainder theorem. The following values are precomputed and stored as part of the private key:. This is more efficient than computing exponentiation by squaring even though two modular exponentiations have to be computed. The reason is that these two modular exponentiations both use a smaller exponent and a smaller modulus.

The security of the RSA cryptosystem is based on two mathematical problems: Full decryption of an RSA ciphertext is thought to be infeasible on the assumption that both of these problems are hard, i. Providing security against partial decryption may require the addition of a secure padding scheme.

The RSA problem is defined as the task of taking e th roots modulo a composite n: Currently the most promising approach to solving the RSA problem is to factor the modulus n. With the ability to recover prime factors, an attacker can compute the secret exponent d from a public key n , e , then decrypt c using the standard procedure.

No polynomial-time method for factoring large integers on a classical computer has yet been found, but it has not been proven that none exists. See integer factorization for a discussion of this problem. Multiple polynomial quadratic sieve MPQS can be used to factor the public modulus n. The time taken to factor bit and bit n on a desktop computer Processor: Intel Dual-Core iU 1. A tool called YAFU can be used to optimize this process.

Just less than five gigabytes of disk storage was required and about 2. Rivest, Shamir, and Adleman noted [2] that Miller has shown that — assuming the truth of the Extended Riemann Hypothesis — finding d from n and e is as hard as factoring n into p and q up to a polynomial time difference.

Its factorization, by a state-of-the-art distributed implementation, took around fifteen hundred CPU years two years of real time, on many hundreds of computers.

No larger RSA key is known publicly to have been factored. In practice, RSA keys are typically to bits long. Some experts believe that bit keys may become breakable in the near future or may already be breakable by a sufficiently well-funded attacker, though this is disputable. Few people see any way that bit keys could be broken in the foreseeable future. Therefore, it is generally presumed that RSA is secure if n is sufficiently large. If n is bits or shorter, it can be factored in a few hours in a personal computer , using software already freely available.

Mais essentiellement parce que toute autre méthode est plus productive, donc ils sont formés à utiliser à peu près tout sauf regarder le code source. Et bien sûr, ils se sont habitués à la vitesse. Je sais pertinemment que la programmation C est un atout important à avoir. Car voilà la seconde partie de la vérité: Maintenant, imaginez les débutants.

Et malgré cela, ils ont plus de choses que nous à apprendre. Mais sans les y former, et si possible sans les payer trop cher. Ils sont très rapides, mais connaissent tout sur rien. Ils peuvent écrire des fonctions complexes, implémenter des algorithmes tordus, mais sans avoir la moindre idée du but final de la chose.

Résultat 2 ans plus tard je me sers encore des docs, bien entendu, mais un coup d oeil aux sources est devenu pour moi indispensable, ça force a la compréhension de la lib, bien plus enrichissant que de copier coller! La seconde, fouiner sur un irc ou sur SO et ne pas vraiment obtenir la reponse qui te satisfait. En effet, le post est vrai et pertinent. On vit ds un monde malheureux où il faut produire, tout et tout de suite, autrement tu es mis sur le banc de touche. Merci pr le tres bel article.

Je profite de cet article et je vous propose de copier coller le lien suivant et de le ressortir en temps voulu:. Je sais par exemple à peu près écrire en C.

Programmeur PHP, je suis un très gros lecteur de code source. Les débats sur la qualité du code de telle appli par rapport à telle appli sont très courant dans la communauté PHP voir Joomla vs Drupal vs WordPress.

Mais, ce réflexe devrait être le même pour quiconque travaillant dans le domaine des webapps: Ensuite, pour ce qui est de la question de la jeune génération, je pense que les choses sont claires: Du coup as-tu la réponse du mec à ton commentaire? Par contre, ça reste difficile pour moi de comprendre entièrement le code des autres.

Je suis curieux de savoir si vous avez des méthodes. Généralement, je commence par une fonction, et je descend dans le code avec les appels successifs des fonctions internes.

De quoi tu me parles, je veux accéder à une simple variable!! Connaître le protocole HTTP pour débuguer? Je viens de lire les précédents commentaires, et ça me rappelle mes cours de philosophie des mathématiques, où on se demandait ce qui faisait la différence entre les simples connecteurs logiques et le reste des fonctions mathématiques, et pourquoi ce sous ensemble de connecteurs est considéré comme propre à la logique, et pas les autres….

De même, connaitre le SQL est de moins en moins nécessaire. Il y a peu, certains étaient contre la programmation objet car trop gourmande en mémoire. Un codeur de 50 ans, ça ne devrait pas exister. Au passage, profiter de votre cerveau encore plastique pour vous mettre sérieusement au JavaScript.

Mais quelle solution proposez-vous? Tu en as besoin pour trouver du boulot facilement tout de suite, mais pas pour trouver du boulot demain. Je te conseille donc, perso, de laisser totalement tomber le bas niveau, de ne pas consacrer trop de temps aux vieux frameworks type Django, Symfony, JEE, ou. Orcale peut éclater de rire. PS pour les lecteurs: La 1ère version de php a été écrite en c il y a 20 ans déjà?! Donc la génération actuelle doit apprendre le vieux paradigme bientôt périmé, et se préparer au prochain paradigme pas tout à fait prêt.

Google nous facilite la tâche, avec Polymer par exempel:. JS , de express. Au lieu de perdre votre temps à optimiser les clés relationnelles de votre table, apprenez le NoSQL.

Le JavaScript est en passe de devenir LE langage de programmation, le langage de script qui va relayer la programmation C à sa fonction première: Google nous facilite la tâche, avec Polymer par exemple:. Ce changement devrait se produire dans les 10 ans. Donc certes, JS et NoSQL vont continuer de progresser, certes, ce sont des technologies à apprendre, mais non, les autres ne vont pas disparaitres.

Ca sera pareil pour le JS. Ou comment rêver des genoux! Tu traînes trop sur korben. Tu dis des betises à longueur de post ;. On va bien rigoler! Putain franchement, le web 2.