şifr

/ʃifr/

Cases

SingularPluralWhen to use it
nominativeşifrthe cipherşifrlethe ciphersthe plain dictionary form — the doer of the sentence
genitiveşifrnithe cipher'sşifrlenithe ciphers'the owner — whose it is
accusativeşifrnithe cipher (as the object)şifrlenithe ciphers (as the object)a specific, known object — whom or what
dativeşifrgeto the cipherşifrlegeto the ciphersdirection or recipient — to where, to whom
locativeşifrdeat / in the cipherşifrledeat / in the cipherswhere it is; also having — mende bar, "I have it"
ablativeşifrdenfrom the cipherşifrledenfrom the cipherswhere it comes from; also "than" when comparing
When to use each case
nominative
the plain dictionary form — the doer of the sentence
genitive
the owner — whose it is
accusative
a specific, known object — whom or what
dative
direction or recipient — to where, to whom
locative
where it is; also having — mende bar, "I have it"
ablative
where it comes from; also "than" when comparing

The endings are the same ones the pronouns wear — that page explains when each case is used.

With an owner

One ownedSeveral owned
myşifrimmy cipherşifrlerimmy ciphers
yourşifringyour cipherşifrleringyour ciphers
his / herşifrihis / her cipherşifrlerihis / her ciphers
ourşifribizour cipherşifrleribizour ciphers
you all'sşifrigizyou all's cipherşifrlerigizyou all's ciphers
theirşifrleritheir cipherşifrleritheir ciphers

The overlap in the last rows is real, not a mistake: şifrleri can mean "his / her ciphers", "their cipher", or "their ciphers" — context decides.