I've read and I discovered that it's not possible to derive the public key from the public address because of the hashing algorithm.... But is/are there any alternate way/ways that it can be calculated that the restriction may probably be time complexity like brute forcing for the private key in ECDSA? What I actually mean is that to find a private key you'll have to brute force which is actually impossible because of the time complexity. Is there any way to break the SHA256 and RIPEMD-160 to get the public key?
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2$\begingroup$ The question does not define "public address", which is not a standard term in cryptography. Independently, it is tagged encryption, but no encryption is alluded to. Please make it clearer. $\endgroup$– fgrieu ♦Oct 12, 2020 at 11:22
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$\begingroup$ When i wrote encryption i meant the SHA256 and the RIPEMD160 encryption algorithm $\endgroup$– Dave KentOct 12, 2020 at 21:47
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$\begingroup$ SHA-256 and RIPEMD160 are cryptographic hash functions or algorithms, also called message digests or just digests. They are NOT encryption algorithms, also called cipher algorithms or just ciphers. That's why the tag descriptions call them hashes NOT ciphers or encryption algorithms. $\endgroup$– dave_thompson_085Oct 12, 2020 at 23:31
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$\begingroup$ Thanks a lot Dave... I appreciate $\endgroup$– Dave KentOct 13, 2020 at 1:41
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1 Answer
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The "public address" is not a standard cryptographic notion (except perhaps in some subfield like cryptocurrency), and no context is given. That makes the most sensible way to rephrase the question:
Can a public key be found from its SHA-256 or RIPEMD-160 hash?
No, for any public-key cryptosystem, and absent other information (e.g. a list of public keys or private keys actively used). Argument: in any secure public-key cryptosystem, there are so many possible public keys that it's hopeless to try them all; but for secure hashes, including SHA-256 and (AFAIK) RIPEMD-160, that's the only hope to find a first-preimage.
Update: hashing is not encryption. Encryption implies intention that with the appropriate secret or private key, it is easy to invert the encryption and get back to the plaintext. In cryptographic hashing, there's no key (unless specified explicitly: pepper for password hashing), and the only method expected to revert the process is to guess the exact original input.
