56 lines
1.3 KiB
Plaintext
56 lines
1.3 KiB
Plaintext
note
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description: "Output Feedback decryption mode"
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author: "Colin LeMahieu"
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date: "$Date$"
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revision: "$Revision$"
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quote: "Sometimes it is said that man cannot be trusted with the government of himself. Can he, then, be trusted with the government of others? - Thomas Jefferson (1801)"
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class
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OFB_DECRYPTION
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inherit
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ARRAY_FACILITIES
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create
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make
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feature
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make (target_a: OFB_TARGET iv: SPECIAL [NATURAL_8] iv_offset: INTEGER_32)
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require
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iv.valid_index (iv_offset)
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iv.valid_index (iv_offset + target_a.block_size - 1)
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do
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target := target_a
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create last.make_filled (0, block_size)
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last.copy_data (iv, iv_offset, 0, block_size)
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end
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feature
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block_size: INTEGER_32
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do
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result := target.block_size
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end
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decrypt_block (in: SPECIAL [NATURAL_8] in_offset: INTEGER_32 out_array: SPECIAL [NATURAL_8] out_offset: INTEGER_32)
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require
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ofb_ready
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in.valid_index (in_offset)
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in.valid_index (in_offset + block_size - 1)
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out_array.valid_index (out_offset)
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out_array.valid_index (out_offset + block_size - 1)
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do
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target.encrypt_block (last, 0, out_array, out_offset)
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last.copy_data (out_array, out_offset, 0, block_size)
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array_xor (last, 0, in, in_offset, out_array, out_offset, block_size)
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end
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ofb_ready: BOOLEAN
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do
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result := target.ofb_ready
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end
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feature {NONE}
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last: SPECIAL [NATURAL_8]
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target: OFB_TARGET
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end
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