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A simple question :

1, public key - for message encryption
2, private key - for message decryption

in digital signature
1, private key - encrypt hashed value
2, public key - decrypt hashed value

In my understanding public key is strictly for message encryption, and private key is strictly for message decryption only

as described what happens in digital signature confuses me.
public key is able to decrypt message as well ?

is it the difference between private and public key not as clear cut as 1 is strictly for encryption and another for decryption ?

Gilles 'SO- stop being evil'
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user3359026
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    Usually the private and public key only differ in one way: you decide which of the pair to publish and which to keep private. Either key can encrypt data, and either key can decrypt what the other one encrypted. Encrypting data and signing data are different use cases and require different uses of the respective key. – mkl Mar 19 '14 at 15:55
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    I'd like to add that digital signing can only be understood as decrypting a hash if you are using a commutative crypto system like RSA where enc(dec(m))=dec(enc(m))=m. There are many signature systems, for example DSA, that work completely different. – Perseids Apr 11 '14 at 23:27
  • Possible duplicate of [What is the difference between encrypting and signing in asymmetric encryption?](https://stackoverflow.com/questions/454048/what-is-the-difference-between-encrypting-and-signing-in-asymmetric-encryption) – Gilles 'SO- stop being evil' Mar 19 '19 at 01:05

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