There are two lines of coded text in this entry; each line is followed by an inscription of the date "Janury 6th 1842." No known key code exactly deciphers Brigham Young's coded text. Known nineteenth-century keys fit parts of the text closely but do not work to perfectly decode Young's text without modifications. Using a Masonic code key published in 1852, Andrew Ehat has deciphered the first line to read, "I was taken into the lodge." If Ehat's reading is correct, the entry may relate to a petition by Young, Joseph Smith, Willard Richards, and several others on 30 December 1841 for initiation into the Nauvoo Masonic Lodge, which was then not yet formally recognized. The Nauvoo lodge met on 6 January 1842 (the date of Young's coded journal entry) and again on 3 February 1842, when "the Committee of Investigation then reported favorably on the following persons; to wit: Joseph Smith, Willard Richards, Brigham Young," among others. The Nauvoo lodge gained official status on 15 March 1842.

Using the same 1852 key, Ehat has deciphered the second line of coded text to read, "J Smith was Agneww," or, alternatively, "J Smith was Agness." Ehat and others suggest that the entry is a cryptic record of a plural marriage between Joseph Smith and Agnes Coolbrith Smith, the widow of Smith's brother Don Carlos, in the Nauvoo Masonic Hall (though the hall had not yet been built). This interpretation, however, requires the addition of several words to the text or, as Todd Compton has suggested, reading "was" in the cipher text as a code for the phrase "wedded and sealed," a phrase unattested in other sources describing plural marriages of the time. Moreover, if this attests a ceremony uniting Joseph Smith and Agnes Smith, it would not have been a sealing for eternity since Agnes would have been sealed to her deceased husband Don Carlos.

These two lines of coded text are the only known instance of Brigham Young using a cipher or code in any of his writings. (Compton, Plural Wives of Joseph Smith, 153-54; Andrew F. Ehat, "Deciphering the code in the Brigham Young Diary entry for January 6, 1842," unpublished research report, 21 December 2021, Joseph Smith Institute; Nauvoo Masonic Lodge, Minutes, 30 December 1841, 7, CHL; and Freemasons Minutebook, 6, CHL.)