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Let $X$ denote a Hilbert space. Given a compact subset $K$ of $X$ and twocontinuous functions $f:K\to\mathbb{R}$, $G:K\to X$, we show that a necessaryand sufficient condition for the existence of a convex function $F\in C^1(X)$such that $F=f$ on $K$ and $\nabla F=G$ on $K$ is that the $1$-jet $(f, G)$satisfies (1) $f(x)\geq f(y)+ \langle G(y), x-y\rangle$ for all $x, y\in K$,and (2) if $x, y\in K$ and $f(x)= f(y)+ \langle G(y), x-y\rangle$ then$G(x)=G(y)$. We also solve a similar problem for $K$ replaced with an arbitrarybounded subset of $X$, and for $C^1(X)$ replaced with the class$C^{1,u}_{b}(X)$ of differentiable functions with uniformly continuousderivatives on bounded subsets of $X$.

Convex $C^1$ extensions of $1$-jets from compact subsets of Hilbert spaces