A private key is a secret, generated in a random manner string that consists of letters and numbers. Each private key has a matching public key; they are used in cryptographic algorithms. It has two important uses: decrypting messages that were encrypted with the matching public key and digitally signing transactions or messages to prove they're genuine. Safeguarding the private key is vital because if someone gets hold of it, they can access the associated digital assets or pretend to be the key owner.