What is Private Key Encryption?

Question

Cryptography

With asymmetric encryption, according to Wikipedia, different keys are used for encryption and decryption - that's why encryption is called asymmetric.
The public key is used for encryption and can be freely transferred.
The private key is used for decryption and must be kept secret.
This is exactly what happens when data is encrypted in open data channels, and everything is clear here.
Now, what is written about the creation of an EDS. The document (or its hash) is encrypted with a private key to create a signature. And anyone who has the public key can decrypt the encrypted document (or its hash) with that public key. Should get the original document (or its hash).
Now the question is: how is it possible to encrypt a document with a private key? And how can you decrypt with the public key? Exactly in all sources - at least on Wikipedia and around it - exactly the opposite is said: the public key encrypts, the private key decrypts.

Answer 1

Open/closed - publicity status of the key.
Encryption is called asymmetric not because something is open there, but something is closed, but because one key from a pair is used for encryption, and the second is used for decryption.
The keys themselves do not differ in any way for the algorithm, there is no binding that the open one encrypts, the closed one decrypts.
You need to understand this phrase like this - RSA does not matter whether you called the first or second exponent a public key. You can always encrypt something using the first exponent of a pair and decrypt it using the second exponent of the same pair.

Answer 2

I found on Wikipedia - in a very strange place (the old version of the article about SSL, the newest version is not) the following words:
"Public key encryption uses two keys, public and private, and any of them can be used to encrypt a message. If for encryption If the public key is used to decrypt the message, then the private key must be used to decrypt it, and vice versa.In
such a situation, there are two ways in which keys
can be used: a key that no one but her can read (after all, decryption requires a secret key known only to her).
• Secondly, with the help of the private key, the party that owns the private key can create encrypted messages that can be read by anyone (because decryption requires a public key available to everyone), but at the same time, the reader can be sure that this message was created by the party - the owner of the secret key."
If so, then the question is completely removed (that is, there were simply disagreements in Wikipedia).
Is that so?

Answer 3

There are 2 keys:
1. The key to encrypt the message (KZ).
2. The key to decrypt the message (KR).
The terms "private" (PC) and "public" (PC) key are floating concepts for different cases that indicate the public status of the key.
In the case of an encrypted channel:
KZ is OK
KR is ZK
You give everyone the key to encrypt messages to you, which only you can read in the end.
In the case of a signature:
KZ - this is ZK
KR - this is OK
You give everyone the key to decrypt messages written by you, the key that decrypts your signature will confirm that you are the author of the message.
PS The abbreviations KZ, KR, ZK and OK are taken for convenience.

Answer 4

"Encryption" - encrypt all, decrypt one.
"Signature" - encrypt one, decrypt all.
In an asymmetric algorithm, there are two keys, and they are algorithmically equivalent. You can use the left one for encryption, or the right one. No difference. Then, when decoding, respectively, on the contrary - right and left.
Where the word "one" you substitute the word "closed".
Where the word "all" substitute the word "open".
Open/closed is just the role of the key. You print one of the two on your business card, publish it in a newspaper, register it in a public EDS database. And he is called open.
The public can encrypt them for you to actually encrypt messages to you. And can decipher your message to the public, understanding that only you could encrypt such nonsense. ;-)

Answer 5

The public key is used to encrypt the message and to verify the digital signature . These are two different functions.