javascript RSA 与 AES 加密2016-01-27 00:12:29
说到加密首先我觉得有必要先说一下RSA与AES的区别；
RSA显然更安全，公私钥位数都可以设置很大，安全性这么多年也经受住了考验。
但RSA也不是没有缺点的，由于受素数的制约，造成生成公私钥难度加大，
AES是分组密钥，算法输入128位数据，密钥长度也是128位。用Nr表示对一个数据分组加密的轮数（加密轮数与密钥长度的关系如表1所列）。每一轮都需要一个与输入分组具有相同长度的扩展密钥Expandedkey(i)的参与。由于外部输入的加密密钥K长度有限,所以在算法中要用一个密钥扩展程序(Keyexpansion)把外部密钥K扩展成更长的比特串,以生成各轮的加密和解密密钥。
AES相对于RSA来说安全性下降，由于最近国际上有专家已经声称找到了新的方法使破解AES加密的时间，又缩小了至少1/3，所以又衍生出来了三重AES加密，甚至RSA+AES的组合方式，其实组合方式是最有效的，就是开发效率与难度加大了一些。RSA一般专用来对付简短的数据，面对大数据量需要AES的方式，否则加密耗时过长。
下面分享一下javascript RSA与AES加密库
它支持RSA + AES方法，任意字节长度(228, 1024等)的文本都可以进行加密。内容使用一个公钥进行加密，并且只能用这个密钥进行解密。Cryptico.js 没有依赖任何JS框架进行开发，拥有良好的文档。
下面是原文内容，请参考：
Generating an RSA key pair & public key string
Sam wants to send Matt an encrypted message. In order to do this, he first needs Matt's public key string. A public key pair can be generated for Matt like this:
// The passphrase used to repeatably generate this RSA key.var PassPhrase ="The Moon is a Harsh Mistress.";
// The length of the RSA key, in bits.var Bits =1024;
var MattsRSAkey =cryptico.generateRSAKey(PassPhrase, Bits);Matt's public key string can then be generated like this:
var MattsPublicKeyString =cryptico.publicKeyString(MattsRSAkey); and looks like this:
uXjrkGqe5WuS7zsTg6Z9DuS8cXLFz38ue+xrFzxrcQJCXtVccCoUFP2qH/AQ4qMvxxvqkSYBpRm1R5a4/NdQ5ei8sE8gfZEq7dlcR+gOSv3nnS4/CX1n5Z5m8bvFPF0lSZnYQ23xlyjXTaNacmV0IuZbqWd4j9LfdAKq5dvDaoE=Encrypting a message
Matt emails Sam his public key string. Now Sam can encrypt a message for Matt:
var PlainText ="Matt, I need you to help me with my Starcraft strategy.";
var EncryptionResult =cryptico.encrypt(PlainText, MattsPublicKeyString);EncryptionResult.cipher is the encrypted message, and looks like this:
OOHoAlfm6Viyl7afkUVRoYQv24AfdLnxaay5GjcqpxvEK+dph5kUFZEZIFKovVoHoZbtUMekSbMqHQr3wNNpvcNWr4E3DgNLfMZQA1pCAUVmPjNM1ZQmrkKYHPKvkhmVKaBiYAJGoO/YiFfKnaylLpKOYJZctkZc4wflZcEEqqg=?cJPt71IHcU5c2LgqGXQKcx2BaAbm25Q2Ku94c933LX5MObL9qbTJEVEv29U0C3gIqcdqwMV6nl33GtHjyRdHx5fZcon21glUKIbE9P71NwQ=Decrypting a message
Sam sends his encrypted message to Matt. The message can be decrypted like this:
var CipherText ="OOHoAlfm6Viyl7afkUVRoYQv24AfdLnxaay5GjcqpxvEK+dph5kUFZEZIFKo \ vVoHoZbtUMekSbMqHQr3wNNpvcNWr4E3DgNLfMZQA1pCAUVmPjNM1ZQmrkKY \ HPKvkhmVKaBiYAJGoO/YiFfKnaylLpKOYJZctkZc4wflZcEEqqg=?cJPt71I \ HcU5c2LgqGXQKcx2BaAbm25Q2Ku94c933LX5MObL9qbTJEVEv29U0C3gIqcd \ qwMV6nl33GtHjyRdHx5fZcon21glUKIbE9P71NwQ=";
var DecryptionResult =cryptico.decrypt(CipherText, MattsRSAkey);The decrypted message is in DecryptionResult.plaintext.
Signatures & Public Key IDs
If Sam's RSA key is provided to the cryptico.encrypt function, the message will be signed by him:
var PassPhrase ="There Ain't No Such Thing As A Free Lunch.";
var SamsRSAkey =cryptico.generateRSAKey(PassPhrase, 1024);
var PlainText ="Matt, I need you to help me with my Starcraft strategy.";
var EncryptionResult =cryptico.encrypt(PlainText, MattsPublicKeyString, SamsRSAkey);The public key associated with the signature can be used by Matt to make sure that it was sent by Sam, but there are a lot of characters to examine in the key - it would be easy to make a mistake. Instead, the public key string associated with the signature can be processed like this:
var PublicKeyID =cryptico.publicKeyID(EncryptionResult.publickey);and PublicKeyID would look something like this:
d0bffb0c422dfa3d3d8502040b915248This shorter key ID can be used to uniquely identify Sam's public key more easily if it must be done manually. Moreover, this key ID can be used by Sam or Matt to make sure they have typed their own passphrases correctly.
API Documentation
RSA Keys
cryptico.generateRSAKey(passphrase, bitlength)Generates an RSAKey object from a password and bitlength.
passphrase: string from which the RSA key is generated.
bitlength: integer, length of the RSA key (512, 1024, 2048, 4096, 8192).
Returns an RSAKey object.
cryptico.publicKeyString(rsakey)Returns the public key portion of an RSAKey object in ascii-armoredstring form, which allows it to be used on websites and in text fileswithout fear of corrupting the public key.
rsakey: An RSAKey object.
Returns an ascii-armored public key string.
cryptico.publicKeyID(publicKeyString)Returns an MD5 sum of a publicKeyString for easier identification.
publicKeyString: a public key in ascii-armored string form, as generated by the cryptico.publicKeyString function.
Returns an MD5 sum of the public key string.
Encryption
cryptico.encrypt(plaintext, publicKeyString, signingKey)Encrypts a string with the provided public key. Optionally signs the encrypted string with an RSAKey object.
plaintext: the string to be encrypted.
publicKeyString: The public key string of the recipient.
signingKey: the RSAKey object of the sender.
Returns: status, cipher
status: "success" if encryption succeeded, "failure" if it failed.
cipher: An ascii-armored encrypted message string, optionally signed.
Decryption
cryptico.decrypt(ciphertext, key)Decrypts an encrypted message with the recipient's RSAKey and verifies the signature, if any.
ciphertext: The encrypted message to be decrypted.
key: The RSAKey object of the recipient.
Returns: status, plaintext, signature, publicKeyString
status: "success" if decryption succeeded, "failure" if it failed. Does not reflect the status of the signature verification.
plaintext: The decrypted message.
signature: "unsigned" if there was no signature, "verified" if it is signed and valid, "forged" if the signature fails verification.
publicKeyString: public key string of the signature (presumably the sender). Returned even if the signature appears to be forged.
Encryption Technical Documentation
Key generation
A hash is generated of the user's passphrase using the SHA256 algorithm found at webtoolkit.info. This hash is used to seed David Bau's seedable random number generator. A (seeded) random RSA key is generated with Tom Wu's RSA key generator with 3 as a hard-coded public exponent.
Encryption
A 32-byte AES key is generated with Tom Wu's random number generator. The plaintext message is converted to a byte string and padded with zeros to 16 bytes round. An initialization vector is created with Tom Wu's random number generator. The AES key is expanded and the plaintext message is encrypted with the Cipher-block chaining mode using the jsaes library. The AES key is encrypted with the recipient's public key using Tom Wu's RSA encryption library.
The encrypted AES key and encrypted message are ascii-armored and concatenated with the "?" character as a delimiter. As an example, here is the result of the phrase "Matt, I need you to help me with my Starcraft strategy." encrypted withthe passphrase "The Moon is a Harsh Mistress." used to generate the 1024-bit public key:
EuvU2Ov3gpgM9B1I3VzEgxaAVO/Iy85NARUFZb/h+HrOP72degP0L1fWiHO3RDm5+kWRaV6oZsn91juJ0L+hrP6BDwlIza9x9DBMEsg3PnOHJENG63RXbu0qPZd2xDJY70i44sufNqHZ0mui9OdNIeE8FvzEOzMtFGCqDx1Z48s=?K3lOtQC2w+emoR4W3yvAaslSzTj/ZZIkOu3MNTW8y/OX0OxTKfpsaI6zX6XYrM0MpPruw7on1N6VUMpNQO8KUVYl4clquaibKs0marXPFH4=Signing
When signing the encrypted message, two more pieces of information are attached to the cipher text. The first is the ascii-armored RSA public key of the sender. The second piece of information concatenated with the cipher text isthe signature itself, which is generated with the rsa-sign extension by Kenji Urushima, along with the SHA256 algorithm found at webtoolkit.info. These two pieces of code are also used when verifying the signature.
The signature is concatenated with the public key with the string::52cee64bb3a38f6403386519a39ac91c:: used as the delimiter between theplaintext, the public key of the sender, and the signature:
plaintext::52cee64bb3a38f6403386519a39ac91c::public key of sender::52cee64bb3a38f6403386519a39ac91c::signatureThis concatenated block is then encrypted with CBC AES and concatenated with theencrypted AES key to form the complete encrypted message.
https://github.com/wwwtyro/cryptico
