This post is from a low-reputation account and contains an unverified outbound link. Be cautious before clicking external links.
Dear steemit community,
Do not use any bitcoin doubler websites! these are all scams, there is no such thing as a bitcoin doubler. What they do is ask for you private key (which you should never give to anybody). Some people say: "but they don't have my public key or access to my account" well that is not true. The theory behind that is below the example of a malicious bitcoin doubler.
Below you see an elliptic curve, which means you can transform a private key into a public key but never a public key into a private key.
Read Mastering Bitcoin to learn more: http://chimera.labs.oreilly.com/books/1234000001802/ch04.html#pubkey