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Consider that $B$ wants to send a message $m$ that is digitally signed to $A$. Let the pair of private and public keys for $A$ and $B$ be denoted by ${K_{x}}^-$ and ${K_{x}}^+$ for $x=A, B$, respectively. Let $K_{x}(m)$ represent the operation of encrypting $m$ with a key $K_{x}$ and $H(m)$ represent the message digest. Which one of the following indicates the CORRECT way of sending the message $m$ along with the digital signature to $A$?

1. $\left\{m, {K_{B}}^+(H(m))\right\}$
2. $\left\{m, {K_{B}}^-(H(m))\right\}$
3. $\left\{m, {K_{A}}^-(H(m))\right\}$
4. $\left\{m, {K_{A}}^+(m)\right\}$