Proquints: Readable, Spellable, and Pronounceable Identifiers

Introduction Proquints encode binary data as alternating consonant-vowel letters grouped into five-letter syllables, yielding identifiers that are readable, spellable, and pronounceable. The idea and specific letter tables were first described by Daniel Shawcross Wilkerson in 2009 (). This document does not claim originality for the concept; it reformulates and formalizes the description for archival purposes. While multiple schemes exist for encoding network addresses and other binary data, Proquints aim to provide a unique blend of human-reabability, accessibility, and long-term usability. They reduce transcription errors, are friendlier for non-technical users, and offer mnemonic qualities that can help in educational or operational contexts. Although they may not replace all existing representations, Proquints can serve as a complementary format that improves clarity in documentation, user interfaces, and spoken communication, particularly where accuracy and inclusivity matter.

Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [] [] when, and only when, they appear in all capitals, as shown here.

Format A proquint encodes data in 16-bit blocks. Each block maps to a five-letter syllable of the form CVCVC (Consonant-Vowel-Consonant-Vowel-Consonant). The mapping tables are fixed: Consonants (indices 0..15):

b d f g h j k l m n p r s t v z

Vowels (indices 0..3):

a i o u

Encoding

Encoders MUST process the input as an ordered sequence of 16-bit words formed from the octet string in network byte order (big-endian).
If the input contains an odd number of octets, encoders MUST append a single zero octet (0x00) to complete the final 16-bit word and MUST signal this padding by appending a single trailing hyphen (U+002D HYPHEN-MINUS) to the end of the proquint string. Encoders MUST NOT append a trailing hyphen when the input length is even.
Hyphens between syllables remain optional for readability; decoders MUST ignore interior hyphens. Only a single trailing hyphen has special meaning as a padding signal; multiple trailing hyphens are invalid.
For each 16-bit word, map bits 15-12 to the first consonant, bits 11-10 to the first vowel, bits 9-6 to the second consonant, bits 5-4 to the second vowel, and bits 3-0 to the final consonant.
Concatenate syllables. Hyphens MAY be inserted between syllables for readability; decoders MUST ignore interior hyphens.

Decoding

Decoders MUST reverse the mapping in .
Decoders MUST accept upper- or lower-case input and MUST ignore interior hyphens. If the input ends in a single trailing hyphen, the decoder MUST: (1) decode the syllables to octets; (2) verify that the final octet is 0x00; and (3) remove that final octet. If a trailing hyphen is present and the final octet is not 0x00, the decoder MUST treat the input as invalid.
If no trailing hyphen is present, the decoder MUST NOT remove any trailing octet, even if it is 0x00.
Inputs with multiple trailing hyphens, a trailing hyphen without any syllables, or a length not divisible by five letters (after removing hyphens) MUST be rejected.

Encoding and Decoding Specification

Letter Tables and Indices Proquint encodes each 16-bit word as five letters in the pattern CVCVC (Consonant–Vowel–Consonant–Vowel–Consonant). The mapping tables and indices are fixed and normative. Consonant table (index 0..15): Vowel table (index 0..3):

Bit Layout Each 16-bit input value (bits 15..0, most significant bit first) MUST be mapped to letters in this order: first consonant (C1) bits 11..10 -> first vowel (V1) bits 9.. 6 -> second consonant(C2) bits 5.. 4 -> second vowel (V2) bits 3.. 0 -> third consonant (C3) ]]> Encoders MUST process input as an ordered sequence of 16-bit words formed from the input octet string in network byte order (big-endian): octet[i] contributes bits 15..8 and octet[i+1] contributes bits 7..0 of the word. If the input contains an odd number of octets, encoders MAY pad a single zero octet to complete the final 16-bit word; applications using padding MUST specify how the original length is recovered. Encoders MAY insert ASCII hyphens (0x2D) between syllables for readability. Decoders MUST ignore interior hyphens, but not trailing hyphens which indicate padding.

Encoding Algorithm (Pseudocode) > 12) & 0xF] v1 = vowels [(w >> 10) & 0x3] c2 = consonants[(w >> 6) & 0xF] v2 = vowels [(w >> 4) & 0x3] c3 = consonants[(w ) & 0xF] syllable = c1 + v1 + c2 + v2 + c3 out += syllable // optional: out += '-' between syllables if pad: out += '-' // signal padding present return out ]]>

Decoding Algorithm (Pseudocode) > 8) & 0xFF) out.append( w & 0xFF) if pad: if out[-1] != 0x00: error("final hyphen present, but last byte is not 0x00") out.pop() // remove padding byte return out ]]> Decoders MUST accept input in either case (upper/lower) and MUST reject any character not in the defined consonant/vowel sets (after stripping hyphens). If applications use padding on encode, they MUST specify how to remove any trailing zero octet introduced solely for padding.

Normalization Encoders SHOULD produce lowercase output. Encoders MUST append a single trailing hyphen only when signaling padding (odd input length). Decoders MUST treat input as case-insensitive, MUST ignore interior hyphens, and MUST apply the trailing-hyphen padding rule defined in this document. Encoders and decoders MUST use the tables and ordering defined in and . Substituting letters or re-ordering bits is not Proquint and will not interoperate.

Test Vectors The following vectors are derived directly from this specification and can be used to verify independent implementations. babab 0xFFFF -> zuzuz 0x1234 -> damuh 0xF00D -> zabat 0xBEEF -> ruroz # Two words (32-bit), big-endian byte order: bytes: 0x12 0x34 0xF0 0x0D words: 0x1234, 0xF00D pq: damuh-zabat (with hyphen) or damuhzabat (without) # Raw ASCII example ("F3r41OutL4w"), # UTF-8 bytes, zero-padded to even length: ASCII: 46 33 72 34 31 4F 75 74 4C 34 77 Length: 11 bytes Pad: 00 Words: 0x4633 0x7234 0x314F 0x7574 0x4C34 0x7700 PQ: himug-lamuh-gajaz-lijuh-hubuh-lisab- (interior hyphens optional) # Padding examples # Even-length input (no padding, no trailing hyphen): bytes: 01 02 03 00 words: 0x0102, 0x0300 pq: bahaf-basab (or "bahafbasab" without interior hyphen) out: 01 02 03 00 # Odd-length input with padding signaled by trailing hyphen: bytes: 01 02 03 encoder pads: -> add 00 to form final word 0x0300 pq: bahaf-basab- (trailing hyphen REQUIRED) decoder: decodes to 01 02 03 00, verifies last octet 00, then removes it out: 01 02 03 # Invalid (trailing hyphen but last octet != 00): pq: bahaf-basad- -> decode last word to ... 01 (not 00) => ERROR # Invalid (multiple trailing hyphens): pq: bahaf-basab-- => ERROR ]]> Implementations MUST reproduce these outputs exactly.

Error Handling Decoders MUST fail input that: (1) contains characters outside the defined tables (after interior hyphen removal); (2) has length not divisible by 5 letters; or (3) violates the CVCVC pattern. Error signaling is application-specific but MUST reject invalid input rather than attempt to guess. A trailing hyphen MUST only be used to signal removal of a single trailing 0x00 octet; any other usage is invalid.

Backward Compatibility Implementations that predate this specification’s padding specification may ignore a trailing hyphen and therefore retain the trailing 0x00 octet. To interoperate with such decoders, producers SHOULD avoid relying on padding removal when communicating with unknown peers.

Security Considerations Proquint is a presentation encoding. It provides no confidentiality, integrity, or authentication services. It does not add or remove entropy, and it MUST NOT be used as a cryptographic transform. Use of a trailing hyphen reveals the parity of the original octet length. This leaks at most one bit of information (even vs. odd length), which is unlikely to be security-relevant for typical uses of Proquints.

IANA Considerations This document has no IANA actions.

Acknowledgments The author thanks Daniel Shawcross Wilkerson for originating the proquint concept and publishing the initial specification in 2009 ().