Meanings

social security number (USA)

taxpayer identification number (in the US, Germany, etc.)

flare gun

the first

cryptographic algorithm

pictogram

heliogram

this month's issue (e.g. of a magazine)

long-vowel mark

flat (sign)

policy number

quantum-resistant cryptography

book cipher

end-to-end encryption

end-to-end encryption

section mark

Normanton incident (1886)

cipher-key

autoencoder (neural network)

region code (e.g. for DVDs)