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The ASN.1 BMPString type contains UNICODE characters. They are two-byte characters, and are not recommended for use unless properly subtyped.
greekCapitalLetterSigma BMPString ::= {0,0,3,145}
In BER, the BMPString type values defined in the example above are encoded as follows:
1E 02 0391
The BMPString type can be constrained by a single value, by size constraints, and by permitted alphabet constraints.