MITRE 2013 Writeup : Cryptography 100

Easy one.  File came in the form of a text file:

qnfzvyxfunxrolxrivaynjirezlzvyxfunxroevatfnyyguro
blfgbgurlnequnafcbvagrqqbjagurfgerrgnggurfznyyteb
hcbslbhatzraurnqvatgurvejnltrfghevatjvguuvfpubpby
ngrfunxrjungqnaybbxrqhcsebzuvfynjazbjrenaqjbaqrer
qjulunafxrcgznxvatzvyxfunxrfnaqgurapbzvatgbuvflne
qjvgubhgoevatvatuvzbarpurpxbhgzlzvyxfunxrrrgfoeva
tvatnyygubfroblfgbzllnequnafgubfrneragoblfgurlerg
urlerabgoblfinggurleryvggyrtveyffnlvatgurleryvxrv
gforggregunalbhefchgbalbhetynffrfunafgurlergbbfyb
jgborlbhatzranggenpgrqolnsebmraqnvelonfrqgerngnaq
gurlerzhggrevatfbzrguvatvguvaxgurlzvtugorbhgsbezb
ergunalbhezvyxfunxrcnyinglbhguvaxgurlzvtugorserap
ugursyntvfzpnfrirakfvkkfvkkavarkfvkkfrirakfvkksvi
rkehavguvaxgurlermbzovrfohgmbzovrfqbagyvxrzvyxfun
xrfgurlernyyynpgbfrvagbyrenagiurernerlbhtbvatinvg
invgsbezrqbagyrggurztrgzlzvyxfunxr

Frequency analysis:

r (114) occurs 11.573472041612484 %
g (103) occurs 9.622886866059818 %
v (118) occurs 7.022106631989597 %
n (110) occurs 6.892067620286085 %
u (117) occurs 6.892067620286085 %
a (97) occurs 6.631989596879063 %
b (98) occurs 6.501950585175553 %
f (102) occurs 6.371911573472042 %
e (101) occurs 5.3315994798439535 %
l (108) occurs 4.4213263979193757 %
y (121) occurs 4.031209362808843 %
z (122) occurs 3.77113133940182 %
x (120) occurs 3.2509752925877766 %
t (116) occurs 3.1209362808842653 %
q (113) occurs 2.47074122236671 %
h (104) occurs 2.2106631989596878 %
o (111) occurs 2.2106631989596878 %
k (107) occurs 1.5604681404421327 %
j (106) occurs 1.4304291287386216 %
i (105) occurs 1.3003901170351105 %
p (112) occurs 1.1703511053315995 %
s (115) occurs 1.0403120936280884 %
c (99) occurs 0.7802340702210663 %
m (109) occurs 0.39011703511053317 %

The most common letters are r at 11.5% and g at 9.6%.  "Hey," says you, "that looks like the standard frequency table!)  So it's probably a substitution cipher.  Even better, it's a Caesar cipher.

Rotated 13 letters forward:

DASMILKSHAKEBYKEVINLAWVERMYMILKSHAKEBRINGSALLTHEBOYSTO
THEYARDHANSPOINTEDDOWNTHESTREETATTHESMALLGROUPOFYOUNGM
ENHEADINGTHEIRWAYGESTURINGWITHHISCHOCOLATESHAKEWHATDAN
LOOKEDUPFROMHISLAWNMOWERANDWONDEREDWHYHANSKEPTMAKINGMI
LKSHAKESANDTHENCOMINGTOHISYARDWITHOUTBRINGINGHIMONECHE
CKOUTMYMILKSHAKEEETSBRINGINGALLTHOSEBOYSTOMYYARDHANSTH
OSEARENTBOYSTHEYRETHEYRENOTBOYSVATTHEYRELITTLEGIRLSSAY
INGTHEYRELIKEITSBETTERTHANYOURSPUTONYOURGLASSESHANSTHE
YRETOOSLOWTOBEYOUNGMENATTRACTEDBYAFROZENDAIRYBASEDTREA
TANDTHEYREMUTTERINGSOMETHINGITHINKTHEYMIGHTBEOUTFORMOR
ETHANYOURMILKSHAKEPALVATYOUTHINKTHEYMIGHTBEFRENCHTHEFL
AGISMCASEVENXSIXXSIXXNINEXSIXXSEVENXSIXXFIVEXRUNITHINK
THEYREZOMBIESBUTZOMBIESDONTLIKEMILKSHAKESTHEYREALLLACT
OSEINTOLERANTVHEREAREYOUGOINGVAITVAITFORMEDONTLETTHEMG
ETMYMILKSHAKE

MCA-76696765.  Very simple; took us (and most of the teams) a few minutes to solve.