A private key is a secret piece of data that proves your right to spend bitcoins from a specific wallet through a cryptographic signature. Your private key(s) are stored in your computer if you use a software wallet; they are stored on some remote servers if you use a web wallet. Private keys must never be revealed as they allow you to spend bitcoins for their respective Bitcoin wallet.
A private key is a string of data that shows you have access to bitcoins in a specific wallet. Think of a private key like a password; private keys must never be revealed to anyone but you, as they allow you to spend the bitcoins from your bitcoin wallet through a cryptographic signature.
A secret piece of data that proves one’s right to spend bitcoins from a specific wallet through a cryptographic signature. It is a 256-bit number used in ECDSA algorithm to create transaction signatures to prove ownership of bitcoins. An alphanumeric string kept secret by the user and designed to sign a digital communication when hashed with a public key. In the case of Bitcoin, this string is a private key designed to work with a public key. The public key is a Bitcoin address. This unique identifier code is used as a digital signature during transactions. Compared to public keys, which are openly listed in directories of many cryptocurrency exchanges, private keys are intended to remain closely guarded. A private key is used to “sign” an approval of a transaction. Private keys are stored within wallet applications and are usually encrypted with a pass phrase. Private keys can be completely random or generated from a single secret number In the case of Bitcoin, a Bitcoin wallet and its private key(s) are linked by mathematics. When one’s Bitcoin software signs a transaction with the appropriate private key, the entire network can see that the signature matches the bitcoins being spent. However, there is no way for others to guess a private key. To maintain integrity and to protect against theft, a private key should never been revealed to others and should be treated as one’s credit card or Social Security numbers.
Malone, J.A (2015). Glossary of Bitcoin Terms and Definitions. United States: Lulu Press, Inc