问题描述
我想知道，如果每次运行生成的哈希值都不相同，那么BCrypt如何推断出输入密码的正确性?
I wonder how BCrypt can infer the correctness of a entered password, if the generated hash is different for each run?
示例:
输入密码:"password123"
Given password: "password123"
让我们说，我将给定的密码哈希10次并收到:
Lets say, I hash the given password 10 times and receive:
$2a$10$Uw0LDj343yp1tIpouRwHGeWflT3.QjDp9DeJ2XiwTIHf1T.pjEy0i
$2a$10$uYWUCEnh4gn00w57VSrYjej.UvhzBL8Wf2doTAGSGfhUMtuGr5bha
$2a$10$cJi3XOkRxxicDjEBibNhNOg5MGM.G/.p70KE75.44ayPQo8kCDxUu
$2a$10$qLcN2obMThH544U967JM5OS0vtcfP.Iq1.f0mZdvWfyeIoWHyr422
$2a$10$5/JssXqJyGHeMQlB4pr7zebTRFSt/2iwYJHF5f7.jdlTxbH4c9Sjq
$2a$10$La1UQKu306aNWkhhfhC5XeX7mfcnfbSchBIpLG6O57gur/U/n/fua
$2a$10$xTzEGVfc1D1UHFeMO95ktOJGFT79ybKUKN.z.MidMjP1XfAeElNEi
$2a$10$i9Y.1Ix6PL1bDwoTYtC49.Y0LKpar/S5qC1SkzFB4vnafikOhHSga
$2a$10$FJNTj5xeVbIcMaf9EhodHu9jJLrJL53QHQK9OuemwMh3WuTfxXEqu
$2a$10$OXMToK5CXeNtRHC3w7eqe.Mr7p4fJanbE28E2Y3MHh6f6cq1chyE6
如果我们假设我将第一个哈希存储在数据库中，并且用户尝试在数小时后使用正确的密码登录.用户尝试登录时生成的哈希与我存储在数据库中的哈希完全不同.
If we assume that I store the first hash in my database and a user tries to log in a few hours later with correct password. The hash, which is generated while the user tries to log in, is totally different to the hash I have stored in my database.
BCrypt如何确定两个散列是否引用相同的密码?
How does BCrypt determine whether the two hashes refer to the same password?
推荐答案
示例中的哈希值包含进行验证所需的所有必要信息:
The hash-values in your example contain all the necessary information to do the verification:
$2y$10$nOUIs5kJ7naTuTFkBy1veuK0kSxUFXfuaOKdOKf9xYT0KKIGSJwFa
| | | |
| | | hash-value = K0kSxUFXfuaOKdOKf9xYT0KKIGSJwFa
| | |
| | salt = nOUIs5kJ7naTuTFkBy1veu
| |
| cost-factor = 10 = 2^10 iterations
|
hash-algorithm = 2y = BCrypt
如您所见，该字符串包含算法，成本因素和费用.使用这些参数，您可以从登录密码计算可比较的哈希值.在PHP中，您可以使用函数 password_verify()来验证密码，它将提取密码成本因素和盐分会自动增加.
As you can see, this string contains the algorithm, the cost factor and the salt. With these parameters you can calculate a comparable hash value from the login password. In PHP you can use the function password_verify() to verify the password, it will extract the cost factor and the salt automatically.
// Check if the hash of the entered login password, matches the stored hash.
// The salt and the cost factor will be extracted from $existingHashFromDb.
$isPasswordCorrect = password_verify($password, $existingHashFromDb);
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