ASN1.RdASN1.decode decodes ASN.1 binary format into
raw format chunks tagged with class types.
ASN1.encode converts structured objects into
ASN.1 binary format.
ASN1.item creates an item - basic object in
structures that can be encoded using ASN1.encode.
ASN1.type extracts the class type from an
ASN.1 item
ASN1.decode(what)
ASN1.encode(what)
ASN1.item(what, type)
ASN1.type(what)object to decode/encode/query
class type of the item (integer value)
This is a suite of low-level tools to deal with ASN.1 (Abstract Syntax
Notation One) binary formats DER, BER and CER. The tools were written
specifically to handle the various DER-encoded key structures so it
provides only a subset of the ASN.1 specification. They are used
internally by the PKI poackage.
ASN1.decode decodes the binary representation (as raw vector)
into individual items. Sequences are convered into lists, all other
objects are retained in their binary form and tagged with the integer
class type - which can be obtained using ASN1.type function.
ASN1.encode expects item (or a list of items) either created
using ASN1.decode or ASN1.item and converts them into
DER binary format.
The result of ASN1.encode(ASN1.decode(x)) will be x if
x was in DER format.
ASN1.decode returns either one item or a list.
ASN1.encode returns a raw vector in DER format.
ASN1.type returns an integer class type
ASN1.item returns an ASN.1 item object
ASN1.encode uses a fixed buffer for encoding which currently
limits the total size of the resulting structure to 1MB.
Only definite length forms are supported. The validity of individual items is not checked.
# generate a small key
key <- PKI.genRSAkey(bits = 512L)
# extract private and public parts in DER format
prv <- PKI.save.key(key, format="DER")
pub <- PKI.save.key(key, private=FALSE, format="DER")
# parse the public key
x <- ASN1.decode(pub)
x
#> [[1]]
#> [[1]][[1]]
#> [1] 2a 86 48 86 f7 0d 01 01 01
#> attr(,"type")
#> [1] 6
#>
#> [[1]][[2]]
#> raw(0)
#> attr(,"type")
#> [1] 5
#>
#>
#> [[2]]
#> [1] 30 48 02 41 00 9b c1 d9 83 20 2d 7b 43 f7 39 ca dd 4d 57 52 57 3f 65 b2 7a
#> [26] 31 7c 48 50 66 2c 74 af e1 02 7e da 00 10 72 93 04 93 7b 9c ad 8c 01 31 6a
#> [51] e9 dc a9 d7 e4 a9 9f 57 5e df 4a 3a 6b 81 60 aa 90 77 81 02 03 01 00 01
#> attr(,"type")
#> [1] 3
#> attr(,"padded.bits")
#> [1] 0
#>
# the second element is the actual key
# as a bit string that's itself in DER
# two integers - modulus and exponent
# Note that this is in fact the pure PKCS#1 key format
ASN1.decode(x[[2]])
#> [[1]]
#> [1] 00 9b c1 d9 83 20 2d 7b 43 f7 39 ca dd 4d 57 52 57 3f 65 b2 7a 31 7c 48 50
#> [26] 66 2c 74 af e1 02 7e da 00 10 72 93 04 93 7b 9c ad 8c 01 31 6a e9 dc a9 d7
#> [51] e4 a9 9f 57 5e df 4a 3a 6b 81 60 aa 90 77 81
#> attr(,"type")
#> [1] 2
#>
#> [[2]]
#> [1] 01 00 01
#> attr(,"type")
#> [1] 2
#>
# encoding it back should yield the same representation since it is DER
stopifnot(identical(ASN1.encode(x), as.raw(pub)))