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There are 64 combinations of three bases and I only need to describe 20, so there's combinations to spare.
三个一组的碱基产生六十四种组合,而我只需对应二十种氨基酸,所以一种氨基酸会对应不同密码子
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Well, not everybody, but everybody can use to keep emails safe, just like sort of a really easy thing to do.
嗯，不一定是所有人，但是每个人都可以轻而易举地用这种密码来保证自己邮箱的安全，
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And cryptography involves scrambling information, converting what you a human can read into sort of nonsense that hopefully a bad guy cannot read.
密码包含不规则的信息，它把我们正常人能读懂的东西转化为,希望坏人读不懂的东西。
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How many combinations of codons are there if there's three bases and four possibilities at each base?
那密码子的组合方式到底有几种呢,三个位点,每个位点四种选择
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I saw the thing that said password.
我看到屏幕上写着请输入"密码"
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I got the idea from a book... by Dan Brown, "Da Vinci Code".
我是从一本书里得到了灵感，是丹·布朗的《达芬奇密码》。
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The answer is I can't. OK, in the simple case of integers I can, but in the case of something more complex like faces or fingerprints or passwords for that matter, it's hard to design a hash function that has completely even distribution, meaning that it takes any input into exactly one output spot.
答案是我不能，好吧,在简单的整数的例子中,我可以做到，但是在一些更复杂的场景中,比如面部，指纹，密码相关的问题中，很难设计一个哈希函数具备完全平均的分配,也就是说，做到对任一输入，可以准确地得到相应的唯一输出,因此在一个哈希问题中。
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And they created this like, really big form of cryptography that everybody uses.
他们发明了每个人都在使用的大型密码。
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There's the Diet Code, this is the weight loss secrets of Leonardo Da Vinci, and you probably didn't know this, but see?
还有减肥密码,这是达芬奇的减肥秘诀,你可能并不知道这个,我们来看看
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or whatever. Like, you know, you're speaking the secret code,
好像你在说密码一样，
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There's just more sequences in a three unit codon than I need for the amino acids.
一个氨基酸对应不止一个密码子,由三碱基所构成的密码子
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One of them has the right sequence of codons to specify the amino acid sequence of the protein, and the other one has a complimentary sequence.
该段带有正确的密码子序列,能够指导氨基酸序列合成蛋白质,另一段则是它的互补序列
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If I only had two per codon I wouldn't have enough.
所以如果每个密码子只有两个碱基不够
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As shown in this cartoon here, again you don't need to know the details of this, but if you're interested in knowing what's the biological bases of the genetic code this is it.
像这个动画里画的那样,这里你也不需要了解细节,不过如果你很有兴趣想知道,遗传密码的生物学基础
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Or a lot of the times when a website is compromised and you're able to steal someone's usernames and passwords, very often are the result of simple little things like this.
很多时候，当要访问的网站被人破坏了,你就有机会窃取别人的账号,和密码，正是因为这样或那样的小疏忽存在,才会导致这种事情频频发生。
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The genetic code is said to be degenerate because I can read in one direction.
遗传密码的这种性质称为简并性,我可以从一个方向去解读
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My cat yesterday actually undid my Yale password last night.
我家"小猫"昨晚把我耶鲁账号的密码给改了
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I hope to work for the National Security Agency doing codes and stuff.
我希望能够在国家安全局工作，和密码打交道。
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Yeah. I don't really know a whole lot of modern cryptography yet
嗯，目前我对现代密码学的了解还不多，
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Fast forward mid-semester when we talk about cryptography and scrambling information, we need the ability to express ourselves in words, not just numbers, and we have that already.
回想一下期中的时候，我们讨论过密码学,和一些不规则信息,我们需要话语来表达自己，而不是数字，其实我们已经有了。
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The next I knew, she had literally typed my password.
然后她就真的帮我输入了"密码"
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It's more complicated in making protein from an RNA strand and that complication is called the genetic code.
而从一条单链RNA翻译为蛋白,这个过程更为复杂,称之为遗传密码
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Well, we'll talk before long about cryptography.
好，我们等下讲讲密码学。
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There's cryptography going on.
这里就使用了密码技术。
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You can brute force it and unfortunately, the so-called Caesar cipher is not very secure because if you assume, for our purposes in English alphabet with 26 characters, say all lowercase for all uppercase, my God, you only have to try like 24, 25, 26 possible rotations until you can figure out what his secret message is.
你可以强行解密但是不幸地是，所谓的凯撒密码不是很安全的,因为如果假设，对于我们的26个字符的字母表,指明所有的小写为大写，我的天，你只要试24，25次，26次就可以解答出,密文的内容。
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This is the codon, this is the anti-codon, there's only one anti-codon that matches this one and that anti-codon is always - occurs in a molecule that has leucine attached to the other side.
这是密码子,这是反密码子,只有一个反密码子与之对应,而反密码子的另一端,总是携带着一个亮氨酸
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That creates a problem in the genetic code in that there's 64 possible sequences but there's only 20 some amino acids, so each amino acid can be specified by more than one codon.
这里有个问题,遗传密码有六十四种可能的序列,而只有二十种氨基酸,因此每种氨基酸都有,不止一种密码子与之对应
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Why are there three bases in a codon?
为什么一个密码子有三个碱基呢
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But in society today, and we'll talk a bit about security topics -- and such throughout the course, for cryptography -- for encrypting things like your credit card information and bank accounts -- you don't use 32 bits, you don't use 64 bits, you generally use 1024 bits, 4,048 bits.
但在当今的社会上，我们将讨论一点安全方面的知识,贯穿整个课程，密码学-,加密一些像信用卡信息,银行账号之类的东西--你不能用32位，你也不能用64位，你通常要使用1024位，4048位。
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So what you'll see in problem set 0 or problem set 1 is that you'll soon have access to what we call the CS50 cloud which is a bunch of servers that live on campus and on which you will all have a username and password.
所以你在习题集0或习题集1上看到的,访问“CS50云“,就是一些校园服务器,你可以注册一个用户名和密码。
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