The following quote is from E. Randolph Richards contribution to this book:
Peter is commonly rejected as the author of 1 Peter for the reasons Ehrman cites:
“Whoever wrote 1 Peter, for example, was a highly educated Greek-speaking Christian who understood how to use Greek rhetorical devices and could cite the Greek Old Testament with flair and nuance. That does not apply to the uneducated, illiterate, Aramaic-speaking fisherman from rural Galilee…”
Ehrman dismisses any influence from a secretary (and presumably others):
And it does not seem possible that Peter gave the general gist of what he wanted to say and that a secretary then created the letter for him in his name, since, first, then the secretary rather than Peter would be the real author of the letter, and second, and even more important, we don’t seem to have any analogy for a procedure like this from the ancient world.
Ehrman is mistaken on both accounts.
First, he is confusing singular authorship with authority. No one disputes that Josephus wrote both Antiquities and The Jewish Wars, even though the Greek in the latter was beyond his skills, as the Loeb editor, H. St. John Thackeray, noted. Josephus acquired collaborators (συνεργοι) for exactly the purpose of turning a first-century, Aramaic-speaking Jew (Josephus) into the author of a finely written Greek document. Why is that not possible for Peter? Josephus remains the author; he was the one who inspired, directed, and then checked and signed off on the work. Cicero notes about a letter of Pompey: “I have never seen anything more Sestian in its style.” Nonetheless Cicero still considers the letter to be from Pompey, not Sestius. Pompey was responsible for the content no matter how much assistance he was provided.
Second, Ehrman claims there is no analogy for using a secretary this way, but there are, for instance, many, many examples of well-written Greek letters from common Egyptian soldiers and farmers. In fact, this assistance was a good reason for hiring a secretary.