Series 1Foundation5 chapters · 47 min
OTP Delivery Fundamentals
What a one-time password actually guarantees, how a code travels from your server to a handset, and how to read the signals carriers send back.
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0/5 completeChapters
- 1
What an OTP really is
A possession proof with an expiry date — and nothing more. Getting the threat model right before writing a line of code.
9 min read
- 2
Send your first OTP
Issue, deliver and verify a code end to end in the live playground, then read what each step is doing.
11 min read
- 3
Delivery reports and status codes
Accepted, sent, delivered, undeliverable, expired: how to interpret DLRs and what to do with each.
10 min read
- 4
Encoding, length and concatenation
Why one emoji can triple your SMS bill, and how GSM-7, UCS-2 and segment headers actually work.
8 min read
- 5
Sender IDs and trust
Alphanumeric IDs, long codes, short codes and toll-free numbers — what each signals to users and carriers.
9 min read