Codespeak

Transmutation
Level: Artificer * 2, Bard * 2, Sorcerer */Wizard * 2
Components: V, S, M (a complex rune inscribed on a slip of paper that is then placed under your tongue)
Casting Time: 1 Standard Action
Range: close (25 ft. + 5 ft./2 levels)
Target: you plus one willing creature per 2 levels, no two of which can be more than 30 ft. apart
Duration: 10 min./level (D)
Saving Throw: None
Spell Resistance: no
  Upon casting this spell, all recipients gain the ability to speak a new language. This language sounds like random, babbling syllables to anyone not under the influence of the spell, but the targets understand each other perfectly. Anyone using codespeak can read and write in this new language as well. Once the spell expires, however, any coded writing suddenly appears as gibberish. If the exact same group of individuals become the targets of a codespeak spell again, cast by the same caster, they can once again read any coded writings. A dedicated codebreaker can crack such writing's code, deciphering it one page at a time with a series of DC 30 Linguistics checks. Comprehend languages doesn't enable a caster to understand the language of another's codespeak spell, but it does reveal that the targets are speaking a magical language. Tongues translates codespeak normally.